AUGUST 4, 2026
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Case File

CVE-2026-39971

HIGH · CVSS 7.2 EPSS 0.26% Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2026-04-15 · Last synced 2026-08-04

CyberRota Analysis

This is a high severity vulnerability with a CVSS score of 7.2. Public exploit code or proof-of-concept references have been detected in its references.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-39971
Severity
HIGH
CVSS
7.2
EPSS
0.26%

Original NVD Description

Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the email sending functionality in include/functions.inc.php inserts $_SERVER['HTTP_HOST'] directly into the Message-ID SMTP header without validation, and the existing sanitization function serendipity_isResponseClean() is not called on HTTP_HOST before embedding it. An attacker who can control the Host header during an email-triggering action such as comment notifications or subscription emails can inject arbitrary SMTP headers into outgoing emails. This enables identity spoofing, reply hijacking via manipulated Message-ID threading, and email reputation abuse through the attacker's domain being embedded in legitimate mail headers. This issue has been fixed in version 2.6.0.

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