CVE-2026-39963
MEDIUM
MEDIUM
Priority: 0.02
BB Relevance:
54/100
Published: 2026-04-15
Modified: 2026-10-26
First seen: 2026-10-29
Status: active
Attack Surface
Network
No Auth
Conf. Impact
Scope Change
CVSS Vector Breakdown
AV:
Network
AC:
High
PR:
None
UI:
Required
S:
Changed
C:
High
I:
Low
A:
None
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.
Weakness Classification (1)
Affected Software (2)
| Vendor | Product | Version |
|---|---|---|
| s9y | serendipity | < 2.6.0 |
| s9y | serendipity | 2.6.0 |
References & Advisories (2)
Product
Exploit
Mitigation
Vendor Advisory