CVE-2026-55767
An attacker-controlled origin that an application requests with a shared cookie jar can therefore set a cookie that Guzzle later sends to unrelated hosts using the same jar.
Does this matter?
Lower severity and a low EPSS score (0.21%). Track it; it rarely justifies an emergency change on its own.
Description
Guzzle is an extensible PHP HTTP client. Prior to 7.12.1, CookieJar incorrectly accepts cookies with a dot-only Domain attribute and whitespace-padded variants. SetCookie::matchesDomain() removes leading dots from the cookie domain, normalizing dot-only values to the empty string; SetCookie::validate() only rejected a strictly empty domain, so these cookies could be stored and the empty normalized domain was treated as matching any request host. An attacker-controlled origin that an application requests with a shared cookie jar can therefore set a cookie that Guzzle later sends to unrelated hosts using the same jar. This may allow cookie injection or session fixation against downstream services, depending on how those services interpret the injected cookie. This vulnerability is fixed in 7.12.1.
- CVSS 3.1
- 5.8 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
- EPSS
- 0.21% probability · 12th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-346, CWE-1286
- Affected
- guzzlephp/guzzle
- Source
- security-advisories@github.com
References
- https://github.com/FriendsOfPHP/security-advisories/blob/master/guzzlehttp/guzzle/CVE-2026-55767.yaml
- https://github.com/guzzle/guzzle/commit/7f537cded1912349abf5081258d6db19106d774d
- https://github.com/guzzle/guzzle/pull/3653
- https://github.com/guzzle/guzzle/releases/tag/7.12.1
- https://github.com/guzzle/guzzle/security/advisories/GHSA-cwxw-98qj-8qjxThird Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.