CVE-2026-55767

guzzle: Guzzle is an extensible PHP HTTP client

CVE-2026-55767 is fixed in guzzle on 1 platform by DEBIAN-CVE-2026-55767 (version 7.12.1-1), released June 25, 2026. It is not reported as exploited. Patch Radar priority: Routine.

Routine
CVSS
5.8
medium
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0021
11th percentile

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.

Where it's fixed

ProductFixed inFixReleased
Linux
guzzle · Debian 14 7.12.1-1 DEBIAN-CVE-2026-55767 Jun 25, 2026

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