> CVE-2026-39971 [HIGH]

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PUBLISHED
2026-04-15 04:17
MODIFIED
2026-04-15 04:17
CVSS_SCORE V3
7.2
EPSS (Prob. Exploit)
0.26%
Top 82.8%
DATA SOURCES:
NVD 🔗 2026-04-15 CWE MITRE 🔗 2026-11-01 FIRST EPSS 🔗 2026-11-08 GITHUB 🔗 2026-11-05 OSV 🔗 2026-11-02

> 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_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> CVSS V3 METRICS

CVSS_VECTOR
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
EXPLOITABILITY
3.9
IMPACT
2.7

> MÉTRIQUES CVSS DÉTAILLÉES

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Métrique Valeur Interprétation
AV (Vecteur d'Attaque)
Attack Vector
Network (N)
Exploit possible à distance via réseau (HTTP, API, etc.)
AC (Complexité d'Attaque)
Attack Complexity
Low (L)
Peu de conditions requises pour exploiter
PR (Privilèges Requis)
Privileges Required
None (N)
Aucune authentification requise
UI (Interaction Utilisateur)
User Interaction
None (N)
Aucune interaction utilisateur nécessaire
S (Périmètre)
Scope
Changed (C)
Impact s'étend au-delà du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
Low (L)
Divulgation limitée d'informations
I (Impact Intégrité)
Integrity Impact
Low (L)
Modification limitée des données possible
A (Impact Disponibilité)
Availability Impact
None (N)
Aucune interruption de service

> RÉSUMÉ DES IMPACTS

Confidentialité
Low
Divulgation limitée d'informations
Intégrité
Low
Modification limitée des données possible
Disponibilité
None
Aucune interruption de service

> WEAKNESSES

CWE-113

> CWE DETAILED DESCRIPTIONS

CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers - The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers.

> GITHUB SECURITY ADVISORY

GHSA-458g-q4fh-mj6r HIGH

Serendipity has a Host Header Injection allows SMTP header injection via unvalidated HTTP_HOST in Message-ID email header

AFFECTED PACKAGES:
COMPOSER / s9y/serendipity
< 2.6.0
Fixed in: 2.6.0

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

Serendipity: Host Header Injection leads to SMTP header injection via unvalidated HTTP_HOST

AFFECTED PACKAGES:
Unknown / Unknown
15 versions affected
ALIASES:
GHSA-458g-q4fh-mj6r

> HISTORIQUE DES MODIFICATIONS

Première apparition
15/04/2026 04:17
Source: NVD
📊 ENRICHISSEMENT 01/11/2026 06:59
CWE
Champ modifié: Description CWE
Ancienne valeur:
CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') - The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.)...
Nouvelle valeur:
CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers - The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or inco...
📊 ENRICHISSEMENT 01/05/2026 06:01
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') - The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.)...
Total des modifications: 2 Dernière mise à jour: 1 week ago

> REFERENCES

https://github.com/s9y/Serendipity/releases/tag/2.6.0
https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6r
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