Vulnerability Description
Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the serendipity_setCookie() function in include/functions_config.inc.php uses $_SERVER['HTTP_HOST'] without validation as the domain parameter of setcookie(). An attacker who can influence the Host header at login time, such as via MITM, reverse proxy misconfiguration, or load balancer manipulation, can force authentication cookies including session tokens and auto-login tokens to be scoped to an attacker-controlled domain. This enables session fixation, token leakage to attacker-controlled infrastructure, and privilege escalation if an admin logs in under a poisoned Host header. This issue has been fixed in version 2.6.0.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| S9Y | Serendipity | < 2.6.0 |
Related Weaknesses (CWE)
References
- https://github.com/s9y/Serendipity/releases/tag/2.6.0Product
- https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gfExploitVendor AdvisoryMitigation
- https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gfExploitVendor AdvisoryMitigation
FAQ
What is CVE-2026-39963?
CVE-2026-39963 is a vulnerability with a CVSS score of 6.9 (MEDIUM). Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the serendipity_setCookie() function in include/functions_config.inc.php uses $_SERVER['HTTP_HOST'] without validation as ...
How severe is CVE-2026-39963?
CVE-2026-39963 has been rated MEDIUM with a CVSS base score of 6.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-39963?
Check the references section above for vendor advisories and patch information. Affected products include: S9Y Serendipity.