Affected: npm: axios

# Vulnerability Disclosure: Unrestricted Cloud Metadata Exfiltration via Header Injection Chain

## Summary The Axios library is vulnerable to a specific gadget-style attack chain in which **prototype pollution** in a third-party dependency may be leveraged to inject unsanitized header values into outbound requests.

Axios can be used as a gadget after pollution occurs elsewhere because header values merged from attacker-controlled prototype properties are not sanitized for CRLF (`\r\n`) characters before being written to the request. In affected deployments, this may enable limited request manipulation or metadata access as part of a higher-complexity exploit chain.

**Severity**: Moderate (CVSS 3.1 Base Score: 4.8) **Affected Versions**: All versions (v0.x - v1.x) **Vulnerable Component**: `lib/adapters/http.js` (Header Processing)

## Usage of \"Helper\" Vulnerabilities This issue requires a separate **prototype pollution** vulnerability in another library in the application stack (for example, `qs`, `minimist`, `ini`, or `body-parser`). If an attacker can pollute `Object.prototype`, Axios may pick up the polluted properties during config merge.

Because Axios does not sanitise these merged header values for CRLF (`\r\n`) characters, the polluted property can alter the structure of an outbound HTTP request.

## Proof of Concept

### 1. The Setup (Simulated Pollution) Imagine a scenario where a known vulnerability exists in a query parser. The attacker sends a payload that…