Executive brief
Guzzle, a popular PHP library for making web requests, contains a flaw in how it handles security cookies for websites identified by IP addresses. An attacker could potentially trick the library into sending sensitive session cookies to the wrong server or inject malicious cookies into a user's session. This could lead to unauthorized access to user accounts or data exposure, particularly in private or development network environments.
Technical details
A vulnerability exists in Guzzle's CookieJar where SetCookie::matchesDomain() incorrectly applies subdomain suffix matching to IP address literals (IPv4, bracketed IPv6, or bare numeric values). Instead of requiring an exact host match as mandated by RFC 6265, Guzzle may send a cookie scoped to an IP like '192.168.0.1' to a look-alike host such as 'evil.192.168.0.1'. Exploitation requires the attacker to have influence over name resolution (e.g., split-horizon DNS or container networks) to resolve the look-alike host. This can result in cookie disclosure, injection, or session fixation. The issue is resolved in version 7.12.3 by enforcing exact matches for IP-based cookie domains.
Affected products
- GuzzleHTTP guzzle < 7.12.3
Timeline
- 2026-06-23: disclosed
- 2026-07-08: advisory: NVD publication date
- 2026-07-20: patched: GitHub Advisory reviewed and updated
References
- https://api.github.com/users/GrahamCampbell
- https://github.com/GrahamCampbell
- https://api.github.com/users/GrahamCampbell/gists%7B/gist_id%7D
- https://api.github.com/users/GrahamCampbell/repos
- https://avatars.githubusercontent.com/u/2829600?v=4
- https://api.github.com/users/GrahamCampbell/events%7B/privacy%7D