CVE-2026-55767
MediumCVSS 5.8Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
Vulnerability in Guzzle (PHP HTTP client) before version 7.12.1 allows incorrect acceptance of cookies with a dot-only Domain attribute or whitespace-padded variants. SetCookie::matchesDomain() removes leading dots, normalizing to an empty string, causing the cookie to match any request host. An attacker can set a cookie in a shared cookie jar that Guzzle later sends to unrelated hosts.
Risk Assessment
Risk includes cookie injection or session fixation in applications using this library, potentially leading to unauthorized data access or session hijacking.
Recommendation
Immediately update Guzzle to version 7.12.1 or later, which includes a fix for this vulnerability.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS