CVE-2026-39963

MEDIUM

6.9

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.

CVE Details

CVSS v3.1 Score6.9

SeverityMEDIUM

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

Attack VectorNETWORK

ComplexityHIGH

Privileges RequiredNONE

User InteractionREQUIRED

Published4/15/2026

Last Modified4/23/2026

Sourcenvd

Honeypot Sightings0

Affected Products

s9y:serendipity

Weaknesses (CWE)

CWE-565

References

https://github.com/s9y/Serendipity/releases/tag/2.6.0(security-advisories@github.com)

https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf(security-advisories@github.com)

https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf(134c704f-9b21-4f2e-91b3-4a467353bcc0)

IOC Correlations

No correlations recorded

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