guzzlehttp/guzzle security advisory

CVE-2026-67355: Guzzle: Host-only cookie scope is not preserved

CVE-2026-67355 is a medium-severity security vulnerability in the PHP package guzzlehttp/guzzle (CVSS 5.9), published 1 August 2026. It is fixed in 7.15.1; earlier versions are affected. It can be exploited without an account.

medium 5.9 published 2026-08-01 · updated 2026-10-08

Affected versions: < 7.15.1
Fixed in: 7.15.1
Newest release: 8.3.1
Severity: Medium · CVSS 5.9
Type: Security issue
CWE-201
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-2026-67355

Access: No account. Anyone who can send a request to an app that uses the affected code.
Conditions: It only works under specific conditions the attacker does not fully control (CVSS rates the attack as high complexity).

CVSS vector (scored by VulnCheck): CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/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-2026-67355 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 7.15.1 or newer.
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "guzzlehttp/guzzle": "^7.15.1" 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-2026-67355.
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 this kind of issue while the upgrade waits. None of it replaces the fix.

If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-67355 advisory

guzzlehttp/guzzle versions before 7.15.1 fail to preserve host-only cookie scope, storing the request host in the Domain field instead of marking cookies as host-only. Attackers controlling child hosts can receive host-only cookies intended only for parent hosts, potentially disclosing session identifiers and authorization tokens when the same cookie jar is reused across trust boundaries.

Description from the CVE record, published by VulnCheck (the CVE Numbering Authority), via the NVD entry for CVE-2026-67355. Advisory title: “Guzzle: Host-only cookie scope is not preserved”.

References

GitHub advisory GHSA-wm3w-8rrp-j577 github.com
Vulncheck security advisory www.vulncheck.com

Other guzzlehttp/guzzle advisories

high CVE-2026-69246: Guzzle: Noncanonical host can bypass host-based checks 2026-08-03
medium CVE-2026-69245: Guzzle: Noncanonical cookie domain keeps subdomain scope 2026-08-03
medium CVE-2026-67354: Guzzle: URI fragments disclosed in redirect Referer headers 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

Need help patching or upgrading? Laskyr does PHP and Laravel security fixes and upgrades. Tell us what you run and we reply with a plan and a price.

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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.