Guzzle: Proxy Credentials Can Be Sent to the Destination Server

Published as "Guzzle: Proxy-Authorization headers can be sent to origin servers"

medium Guzzle · Last reviewed Nov 3, 2026

CVE: CVE-2026-67339
GHSA: GHSA-94pj-82f3-465w
Packagist: PKSA-pwsk-hy21-4gby
Reported: Jul 20, 2026

Can send Proxy-Authorization credentials to the target server when a request skips the HTTP proxy, with Guzzle's cURL handlers.

Affected and fixed versions

In guzzlehttp/guzzle. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
Up to 7.14.1	7.14.2	Supported

Upgrade

Run the line for the branch you are on.

composer require guzzlehttp/guzzle:^7.14.2

What this means

Guzzle could send your proxy password, the Proxy-Authorization header, to the website you're requesting instead of only to the proxy. If an attacker runs that website, they can record the credential and use your proxy, or reach places the proxy is trusted to reach.

Who is affected

Apps on guzzlehttp/guzzle before 7.14.2 that set a Proxy-Authorization header on requests, client defaults or middleware. The Guzzle advisory says the header could reach the destination when a request:

goes direct, including with proxy set to ''
skips the proxy because of a no_proxy match
goes through a SOCKS proxy
follows a redirect into one of those routes

Older libcurl builds (before 7.37.0) and Guzzle's stream handler had related leaks. Apps that never set a Proxy-Authorization header aren't affected, and neither is CURLOPT_PROXYUSERPWD.

What to do

Update to 7.14.2 or later. The fix keeps the header away from the destination. Until you can update, stop setting Proxy-Authorization as a header and pass proxy credentials in the proxy URL, such as http://user:[email protected]:8080, or through CURLOPT_PROXYUSERPWD. If the credential may have leaked, change it.

Reported by GrahamCampbell.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Guzzle: Proxy Credentials Can Be Sent to the Destination Server (CVE-2026-67339, GHSA-94pj-82f3-465w)
Details: https://phpnews.net/security/guzzle/ghsa-94pj-82f3-465w

Affected versions, as Composer constraints:
- guzzlehttp/guzzle: <7.14.2

Fixed releases on branches that still get security fixes:
- Up to 7.14.1: update to 7.14.2

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/guzzle/ghsa-94pj-82f3-465w and check whether the project meets the conditions it describes (a feature in use, a config value, a driver). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

← All Guzzle advisories