CVE-2026-39971Serendipity is a PHP-powered weblog engine.
Updated under an hour ago ()
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It affects s9y serendipity. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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Free account, 1 product
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.
- CVSS
- 7.2 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- Weakness (CWE)
- CWE-113
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
s9y serendipity s9y:serendipity | before 2.6.0; 2.6.0 | NVD |
References
- https://github.com/s9y/Serendipity/releases/tag/2.6.0patch
- https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6rexploit, mitigation, vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.