CVE-2026-67320

axios in a Node.js deployment using the HTTP adapter can route requests through an attacker-controlled proxy. axios hardens merged request configuration by creating a null-prototype object, but request interceptors run after the merge; a common immutable interceptor pattern such as {...config} or Object.assign({}, config) converts the hardened config back into a regular object. axios then dispatches that object without re-hardening it, and the Node HTTP adapter reads config.proxy through the prototype chain. If an attacker can pollute Object.prototype.proxy, affected requests can be routed through an attacker-controlled proxy. For plaintext HTTP requests, the proxy can observe Authorization headers, Basic auth from config.auth, method, absolute URL, Host, and request body, and can return its own response. This does not establish browser impact or HTTPS header/body disclosure under normal TLS validation. Affected versions are >=0.31.1 (fixed in 0.33.0) and >=1.15.2 (fixed in 1.18.0).

axios in a Node.js deployment using the HTTP adapter can route requests through an attacker-controlled proxy. axios hardens merged request configuration by creating a null-prototype object, but request interceptors run after the merge; a common immutable interceptor pattern such as {...config} or Object.assign({}, config) converts the hardened config back into a regular object. axios then dispatches that object without re-hardening it, and the Node HTTP adapter reads config.proxy through the prototype chain. If an attacker can pollute Object.prototype.proxy, affected requests can be routed through an attacker-controlled proxy. For plaintext HTTP requests, the proxy can observe Authorization headers, Basic auth from config.auth, method, absolute URL, Host, and request body, and can return its own response. This does not establish browser impact or HTTPS header/body disclosure under normal TLS validation. Affected versions are >=0.31.1 (fixed in 0.33.0) and >=1.15.2 (fixed in 1.18.0).

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-gcfj-64vw-6mp9. This link is maintained to preserve external references.

Original Description

axios in a Node.js deployment using the HTTP adapter can route requests through an attacker-controlled proxy. axios hardens merged request configuration by creating a null-prototype object, but request interceptors run after the merge; a common immutable interceptor pattern such as {...config} or Object.assign({}, config) converts the hardened config back into a regular object. axios then dispatches that object without re-hardening it, and the Node HTTP adapter reads config.proxy through the prototype chain. If an attacker can pollute Object.prototype.proxy, affected requests can be routed through an attacker-controlled proxy. For plaintext HTTP requests, the proxy can observe Authorization headers, Basic auth from config.auth, method, absolute URL, Host, and request body, and can return its own response. This does not establish browser impact or HTTPS header/body disclosure under normal TLS validation. Affected versions are >=0.31.1 (fixed in 0.33.0) and >=1.15.2 (fixed in 1.18.0).

Summary

Axios’ Node.js HTTP adapter can route requests through an attacker-controlled proxy when Object.prototype.proxy is polluted and request configuration is materialized as a regular object before dispatch.

Recent axios releases harden merged request config by creating a null-prototype object. However, request interceptors run after that merge and may return a replacement config. A common immutable interceptor pattern such as {...config} or Object.assign({}, config) converts the hardened config back into a normal object. Axios then dispatches that object without re-hardening it, and the Node HTTP adapter reads config.proxy through the prototype chain.

Impact

In a Node.js deployment using the HTTP adapter, an attacker who can trigger prototype pollution elsewhere in the process can route affected HTTP requests through an attacker-controlled proxy.

The highest confirmed impact is for plaintext HTTP requests. The proxy can observe explicit Authorization headers, axios-generated Basic auth from config.auth, request method, absolute URL, Host, and request body content. The proxy can also return its own response to axios for the affected request.

This does not establish browser impact. It also does not establish HTTPS header or body disclosure under normal TLS validation.

Affected Functionality

Affected functionality is limited to axios requests that use the Node.js HTTP adapter, including default Node usage when the HTTP adapter is selected and explicit adapter: 'http' usage.

The relevant configuration path is config.proxy in the Node HTTP adapter. The hardened-bypass path requires a request interceptor such as:

api.interceptors.request.use((config) => ({
  ...config,
  headers: {
    ...config.headers,
    'X-App': 'demo'
  }
}));

Unaffected or mitigating conditions include browser adapters, the Node fetch adapter, no polluted Object.prototype.proxy, an own proxy: false or safe own proxy value on the config, and hardened releases where interceptors return the original null-prototype config instead of a regular object clone.

Technical Details

lib/core/mergeConfig.js creates a null-prototype merged config and uses own-property reads for merged values. This is intended to prevent polluted Object.prototype values from affecting config behavior.

lib/core/Axios.js runs request interceptors after the merge. In both the asynchronous and synchronous interceptor paths, axios passes the interceptor-returned config into dispatch.

lib/core/dispatchRequest.js accepts that returned config, transforms request data, selects the adapter, and calls the adapter without re-hardening or re-normalizing the config.

lib/adapters/http.js uses own-property reads for several sensitive fields, but the initial proxy dispatch path still passes config.proxy directly into setProxy(). If an interceptor returned a regular object, config.proxy can resolve to inherited Object.prototype.proxy.

Proof of Concept of Attack

import axios from './index.js';
import http from 'node:http';

for (const key of [
  'HTTP_PROXY', 'HTTPS_PROXY', 'ALL_PROXY',
  'http_proxy', 'https_proxy', 'all_proxy',
  'NO_PROXY', 'no_proxy'
]) {
  delete process.env[key];
}

const listen = (handler) => new Promise((resolve, reject) => {
  const server = http.createServer(handler);
  server.once('error', reject);
  server.listen(0, '127.0.0.1', () => resolve(server));
});

const close = (server) => new Promise((resolve) => server.close(resolve));

const targetHits = [];
const proxyHits = [];

const target = await listen((req, res) => {
  targetHits.push(req.url);
  res.end('target');
});

const proxy = await listen((req, res) => {
  let body = '';
  req.on('data', (chunk) => body += chunk);
  req.on('end', () => {
    proxyHits.push({
      url: req.url,
      authorization: req.headers.authorization,
      host: req.headers.host,
      body
    });
    res.setHeader('content-type',…

axios in a Node.js deployment using the HTTP adapter can route requests through an attacker-controlled proxy. axios hardens merged request configuration by creating a null-prototype object, but request interceptors run after the merge; a common immutable interceptor pattern such as {...config} or Object.assign({}, config) converts the hardened config back into a regular object. axios then dispatches that object without re-hardening it, and the Node HTTP adapter reads config.proxy through the prototype chain. If an attacker can pollute Object.prototype.proxy, affected requests can be routed through an attacker-controlled proxy. For plaintext HTTP requests, the proxy can observe Authorization headers, Basic auth from config.auth, method, absolute URL, Host, and request body, and can return its own response. This does not establish browser impact or HTTPS header/body disclosure under normal TLS validation. Affected versions are >=0.31.1 (fixed in 0.33.0) and >=1.15.2 (fixed in 1.18.0).

axios in a Node.js deployment using the HTTP adapter can route requests through an attacker-controlled proxy. axios hardens merged request configuration by creating a null-prototype object, but request interceptors run after the merge; a common immutable interceptor pattern such as {...config} or Object.assign({}, config) converts the hardened config back into a regular object. axios then dispatches that object without re-hardening it, and the Node HTTP adapter reads config.proxy through the prototype chain. If an attacker can pollute Object.prototype.proxy, affected requests can be routed through an attacker-controlled proxy. For plaintext HTTP requests, the proxy can observe Authorization headers, Basic auth from config.auth, method, absolute URL, Host, and request body, and can return its own response. This does not establish browser impact or HTTPS header/body disclosure under normal TLS validation. Affected versions are >=0.31.1 (fixed in 0.33.0) and >=1.15.2 (fixed in 1.18.0).