Guzzle: Cookies Set for IP Addresses Leak to Look-Alike Hosts

Published as "Guzzle: Cookie Disclosure and Injection via IP-Address Domains"

medium Guzzle · Last reviewed Nov 3, 2026

CVE: CVE-2026-59883
GHSA: GHSA-g446-98w2-8p5w
Packagist: PKSA-bcdd-5xc7-gwfb
Reported: Jul 20, 2026

Can send cookies scoped to an IP address to other hosts, or let those hosts plant cookies, in apps that use Guzzle's cookie jar.

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 7.12.2	7.12.3	Supported

Upgrade

Run the line for the branch you are on.

composer require guzzlehttp/guzzle:^7.12.3

What this means

Guzzle can send a cookie that was set for an IP address to other hosts whose names end in that address, such as evil.192.168.0.1. A host like that can also plant a cookie that Guzzle later sends to the address itself. Depending on the service, that can leak a cookie, let an attacker inject one, or fix a user's session.

Who is affected

Apps on guzzlehttp/guzzle before 7.12.3 that use Guzzle's cookie support, reuse one cookie jar across more than one host or trust boundary, and hold cookies scoped to an IP address. The Guzzle advisory says names like that can't be registered publicly, so an attacker needs some control over name lookups. That's realistic on private, split-horizon, container or development networks. Apps that don't use Guzzle's cookies, or use a separate jar per host, aren't affected.

What to do

Update to 7.12.3 or later. The fix only sends IP-address cookies back to the exact host. Until you can update, use a separate cookie jar for each host or trust boundary, and avoid new Client(['cookies' => true]) on a client that talks to hosts you trust differently.

Some unusual ways of writing an IP address still got through this fix. See GHSA-f7vp-7xgx-4w4r, fixed in 7.15.2.

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: Cookies Set for IP Addresses Leak to Look-Alike Hosts (CVE-2026-59883, GHSA-g446-98w2-8p5w)
Details: https://phpnews.net/security/guzzle/ghsa-g446-98w2-8p5w

Affected versions, as Composer constraints:
- guzzlehttp/guzzle: <7.12.3

Fixed releases on branches that still get security fixes:
- Up to 7.12.2: update to 7.12.3

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-g446-98w2-8p5w 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