CVE-2026-39963
Serendipity: Host Header Injection enables authentication cookie scoping to an attacker-controlled domain
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.
INFO
Published Date :
April 14, 2026, 11:31 p.m.
Last Modified :
April 14, 2026, 11:31 p.m.
Remotely Exploit :
No
Source :
GitHub_M
Affected Products
The following products are affected by CVE-2026-39963
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Update Serendipity to version 2.6.0 or later.
- Validate Host header inputs.
- Ensure secure cookie configurations.
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CVE-2026-39963 vulnerability anywhere in the article.