guzzlehttp/guzzle security advisory

CVE-2026-69245: Guzzle: Noncanonical cookie domain keeps subdomain scope

CVE-2026-69245 is a medium-severity session fixation vulnerability in the PHP package guzzlehttp/guzzle (CVSS 6.5), published 3 August 2026. It is fixed in 7.15.2 and 8.0.1, one per release line; earlier versions on each line are affected. It can be exploited without an account.

medium 6.5 published 2026-08-03 · updated 2026-09-08

Affected versions: < 7.15.2
>= 8.0.0, < 8.0.1
Fixed in: 7.15.2, 8.0.1
Newest release: 8.3.1
Severity: Medium · CVSS 6.5
Type: Session fixation
CWE-180, CWE-346, CWE-384
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your guzzlehttp/guzzle version affected?

Run composer show guzzlehttp/guzzle in your project, then enter the version. We check it against this and every other known guzzlehttp/guzzle advisory.

Who can exploit CVE-2026-69245

Access: No account. Anyone who can send a request to an app that uses the affected code.

CVSS vector (scored by GitHub): CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Your app is only exposed if it uses the affected part of guzzlehttp/guzzle. The advisory below says which part that is. If you are not sure, upgrade anyway: it costs less than finding out.

How to fix CVE-2026-69245 in guzzlehttp/guzzle

Find the installed version: composer show guzzlehttp/guzzle. If you never required it yourself, composer why guzzlehttp/guzzle shows which package pulls it in.
Update it: composer update guzzlehttp/guzzle --with-all-dependencies. You need the fixed version for your release line (7.15.2 and 8.0.1).
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "guzzlehttp/guzzle": "^8.0.1" if you can take that version), or upgrade the package that requires it.
Run composer audit. It reads the same advisory data and should no longer list CVE-2026-69245.
Commit composer.lock and deploy it. On the server, run composer install --no-dev from the lock file, not composer update.

If you cannot upgrade yet

General hardening for session fixation issues while the upgrade waits. None of it replaces the fix.

Regenerate the session id at login and logout.
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-69245 advisory

Guzzle is an extensible PHP HTTP client. Prior to 7.15.2 and 8.0.1, SetCookie::matchesDomain() gives every subdomain of a cookie Domain that cookie unless SetCookie::matchesDomain() recognizes the Domain as an IP literal or a numeric host, and the decision comes from the domain's own text, so two spellings a transport reads as an address keep subdomain scope. Hexadecimal and mixed-base forms such as 0x7f000001 and 0177.0.0.0x1 go unrecognized while libcurl 8.21.0 reads both as 127.0.0.1. A percent-escaped Domain keeps that scope on both branches because percent-decoding sits above numeric parsing, so 192.168.0.%31 and 127.0.0.1%2e are registered names in the URI grammar rather than address literals, and no numeric rule in any base classifies them, while libcurl decodes the host before resolving and reads them as 192.168.0.1 and 127.0.0.1. A cookie stored for Domain=0x7f000001 is placed in the Cookie header of a request to evil.0x7f000001, disclosing a session identifier or token to a host that is not that address, and a response from evil.0x7f000001 setting Domain=0x7f000001 is accepted into the jar and replayed to the address, so a server answering for the look-alike name can fix a session or set application state. Exploitation requires the application to enable cookie support, address an origin by one of these spellings, and contact a host whose name ends in that spelling. This issue is fixed in versions 7.15.2 and 8.0.1.

Description from the CVE record, published by GitHub (the CVE Numbering Authority), via the NVD entry for CVE-2026-69245. Advisory title: “Guzzle: Noncanonical cookie domain keeps subdomain scope”.

References

GitHub advisory GHSA-f7vp-7xgx-4w4r github.com
Fix commit 3aeea04 github.com
Fix commit 7441019 github.com
Pull request #3907 github.com
Pull request #3908 github.com
Release 7.15.2 github.com
Release 8.0.1 github.com

Other guzzlehttp/guzzle advisories

high CVE-2026-69246: Guzzle: Noncanonical host can bypass host-based checks 2026-08-03
medium CVE-2026-67354: Guzzle: URI fragments disclosed in redirect Referer headers 2026-07-20
medium CVE-2026-67355: Guzzle: Host-only cookie scope is not preserved 2026-07-20
medium CVE-2026-67353: Guzzle: Unbounded response cookies risk denial of service 2026-07-20
medium CVE-2026-59883: Guzzle: Cookie Disclosure and Injection via IP-Address Domains 2026-07-20
medium CVE-2026-67339: Guzzle: Proxy-Authorization headers can be sent to origin servers 2026-07-20

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Where this data comes from

Affected and fixed versions: the Packagist security advisories API (GitHub Advisory Database and FriendsOfPHP), the same data composer audit uses. Synced 2026-11-03.
Description, score, weakness and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
Exploited-in-the-wild status: the CISA Known Exploited Vulnerabilities catalog, checked 2026-11-04.
Compiled by Daniel Lasek at Laskyr from the sources above. The summary, “who can exploit it”, “how to fix it” and hardening sections are our plain-English reading of the record and are generated from it. The quoted description is the record's own text. Spot an error? Tell us.