CVE-2026-55767 Guzzle: Dot-Only Cookie Domains Match All Hosts in guzzlehttp/guzzle

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::valida...

Dot-only cookie domains match all hosts

Impact CookieJar incorrectly accepts cookies with a dot-only Domain attribute, such as Domain=., Domain=.., Domain=..., and whitespace-padded variants such as Domain= . . In affected versions, SetCookie::matchesDomain removes leading dots from the cookie domain, normalizing dot-only values to the...