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CVE-2026-39963 Details

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.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:6.9 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf	CISA-ADP	ExploitMitigationVendor Advisory
https://github.com/s9y/Serendipity/releases/tag/2.6.0	[email protected]	Product
https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf	[email protected]	ExploitMitigationVendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-565	Reliance on Cookies without Validation and Integrity Checking	[email protected]

Affected Products

Product	Versions
s9y serendipity	< 2.6.0 2.6.0 beta1
CPE cpe:2.3:a:s9y:serendipity:::::::: cpe:2.3:a:s9y:serendipity:2.6.0:beta1:::::: Remediation No remediation found in references.

Change History

5 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Apr 23, 2026	Initial Analysis	[email protected]
Apr 15, 2026	CVE Modified	CISA-ADP
Apr 15, 2026	New CVE Received	[email protected]