CVE-2026-55767 (Medium) detected in guzzlehttp/guzzle-7.10.0

[mend-bolt-for-github]

CVE-2026-55767 - Medium Severity Vulnerability

Vulnerable Library - guzzlehttp/guzzle-7.10.0

Guzzle is a PHP HTTP client library

Library home page: https://api.github.com/repos/guzzle/guzzle/zipball/b51ac707cfa420b7bfd4e4d5e510ba8008e822b4

Dependency Hierarchy:

• ❌ guzzlehttp/guzzle-7.10.0 (Vulnerable Library)

Found in HEAD commit: 81f84f058af0cbca57ee22476557ded21c6813aa

Found in base branch: master

Vulnerability Details

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.

Publish Date: 2026-06-23

URL: CVE-2026-55767

CVSS 3 Score Details (5.8)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Changed
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: Low
  • Availability Impact: None

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-cwxw-98qj-8qjx

Release Date: 2026-06-19

Fix Resolution: guzzlehttp/guzzle - 7.12.1

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