CVE-2026-55767
5.8 · MEDIUMOverview
CVE-2026-55767 is a medium-severity vulnerability affecting guzzlephp guzzle. It was published on June 23, 2026 and has a CVSS 3.1 base score of 5.8 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 5.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from guzzlephp. Update guzzle to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| guzzlephp | guzzle | >= 0, < 7.12.1 | Affected |
References
Frequently Asked Questions
What is CVE-2026-55767?
CVE-2026-55767 is a medium-severity vulnerability affecting guzzlephp guzzle. It was published on June 23, 2026 and has a CVSS 3.1 base score of 5.8 (MEDIUM).
How severe is CVE-2026-55767?
This vulnerability has a CVSS 3.1 base score of 5.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-55767?
Check the references section for vendor advisories and patches from guzzlephp. Update guzzle to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-55767?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-55767 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
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Browser-based exploitation validates findings with real proof-of-concept.
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