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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2026-39971 Detail

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.


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://github.com/s9y/Serendipity/releases/tag/2.6.0 GitHub, Inc.
https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6r GitHub, Inc.

Weakness Enumeration

CWE-ID CWE Name Source
CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') GitHub, Inc.  

Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2026-39971
NVD Published Date:
04/15/2026
NVD Last Modified:
04/15/2026
Source:
GitHub, Inc.