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Vulnerabilities

Vulnerability · CVE-2026-39963

Serendipity is a PHP-powered weblog engine.

Published Apr 15, 2026 · catalog updated Jun 17, 2026 · Serendipity is a PHP-powered

Check if you run it

No confirmed exploitation is on record for CVE-2026-39963. EPSS is 0.30%. Act only if a listed version of Serendipity is a PHP-powered is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Serendipity is a PHP-powered).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.9
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.30%
Remediation
Advisory link
Affected products
cpe s9y/serendipity

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe s9y/serendipity2.6.0

How to fix CVE-2026-39963

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-39963. EPSS is 0.30%. Act only if a listed version of Serendipity is a PHP-powered is installed.

Which versions are affected?

Compare what you have installed with 2.6.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-565. EPSS 0.30%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 15, 2026 · NIST NVD

    Detected

    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 authenticati

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 authenticati

Sources

  • CVE.orgVulnerability recordCVE-2026-39963

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-39963

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-39963

    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 head

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.