Guzzle: Redirects Can Leak URL Fragments in the Referer Header

Published as "Guzzle: URI fragments disclosed in redirect Referer headers"

medium Guzzle · Last reviewed Nov 2, 2026

CVE: CVE-2026-67354
GHSA: GHSA-h95v-h523-3mw8
Packagist: PKSA-fy2t-3c5f-827y
Reported: Jul 20, 2026

Can leak secrets kept in a URL fragment to a redirect target, in apps that turn on Guzzle's referer redirect option.

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 7.15.0	7.15.1	Supported

Upgrade

Run the line for the branch you are on.

composer require guzzlehttp/guzzle:^7.15.1

What this means

When Guzzle follows a redirect with its optional referer setting on, it can copy the URL fragment, the part after #, into the Referer header it sends to the new destination. A fragment is never meant to leave the client. If it holds a one-time login secret, an access token or other private data, the redirect target can read it.

Who is affected

Apps on guzzlehttp/guzzle before 7.15.1 that turn on allow_redirects.referer, request a URL with sensitive data in its fragment, and follow a redirect with the same scheme, such as HTTPS to HTTPS, to a less trusted host. The Guzzle advisory notes the referer setting is off by default. Apps that leave it off, keep secrets out of fragments, or don't follow redirects aren't affected.

What to do

Update to 7.15.1 or later. The fix strips the fragment before building the Referer value. Until you can update, keep referer set to false in your redirect options, or remove the fragment before sending a request that may redirect.

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: Redirects Can Leak URL Fragments in the Referer Header (CVE-2026-67354, GHSA-h95v-h523-3mw8)
Details: https://phpnews.net/security/guzzle/ghsa-h95v-h523-3mw8

Affected versions, as Composer constraints:
- guzzlehttp/guzzle: <7.15.1

Fixed releases on branches that still get security fixes:
- Up to 7.15.0: update to 7.15.1

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-h95v-h523-3mw8 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