CVEvulnerability

CVE-2026-39971

7.2 HIGH Published 2026-04-15 Modified 2026-10-26 Official page ↗
Status
Analyzed
Published
2026-04-15
Last modified
2026-10-26
Assigner
[email protected]
CVSS 3.1 ([email protected])
7.2 HIGH — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Weaknesses
CWE-113

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.

Affected configurations

• s9y serendipity (< 2.6.0) • s9y serendipity 2.6.0

Related

Weakness · CWE (1)

  • CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers weakness

References