CVE-2026-39963
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.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
s9y/serendipityPackagist | < 2.6.0 | 2.6.0 |
Affected products
1Patches
Vulnerability mechanics
References
4- github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gfnvdExploitVendor AdvisoryMitigationWEB
- github.com/advisories/GHSA-4m6c-649p-f6gfghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-39963ghsaADVISORY
- github.com/s9y/Serendipity/releases/tag/2.6.0nvdProductWEB
News mentions
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