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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.

PUBLISHED Reserved 2026-04-08 | Published 2026-04-14 | Updated 2026-04-15 | Assigner GitHub_M




MEDIUM: 6.9CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N

Problem types

CWE-565: Reliance on Cookies without Validation and Integrity Checking

Product status

< 2.6.0
affected

References

github.com/...dipity/security/advisories/GHSA-4m6c-649p-f6gf exploit

github.com/...dipity/security/advisories/GHSA-4m6c-649p-f6gf

github.com/s9y/Serendipity/releases/tag/2.6.0

cve.org (CVE-2026-39963)

nvd.nist.gov (CVE-2026-39963)

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