Symfony Vulnerable to Identity Spoofing via Unanchored DN Regex in X509Authenticator
Description
X509Authenticator implements client-certificate (mTLS) authentication: the web server validates the client's certificate against a trusted CA, then passes the certificate's Subject DN (Distinguished Name: a string like CN=Alice,O=Example,emailAddress=alice@example.com) to Symfony via $_SERVER['SSL_CLIENT_S_DN']. Symfony extracts the user identifier from that string.
The extraction uses an unanchored regex that matches emailAddress= anywhere in the DN string: including inside the value of a different RDN (Relative Distinguished Name: one key=value component of the DN), such as CN. An attacker who can obtain a certificate from a trusted CA with a free-text CN can smuggle emailAddress=victim@target inside the CN value and be authenticated as the victim.
Resolution
The X509Authenticator now uses a regex that anchors the match to an RDN boundary (start of string, or following a , / / separator).
The patch for this issue is available here for branch 5.4.
Credits
Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de Composer | symfony/security-http | < 5.4.52, >= 6.0.0-BETA1, < 6.4.40, >= 7.0.0-BETA1, < 7.4.12, >= 8.0.0-BETA1, < 8.0.12 | 5.4.52, 6.4.40, 7.4.12, 8.0.12 |
| Paquete de Composer | symfony/symfony | < 5.4.52, >= 6.0.0-BETA1, < 6.4.40, >= 7.0.0-BETA1, < 7.4.12, >= 8.0.0-BETA1, < 8.0.12 | 5.4.52, 6.4.40, 7.4.12, 8.0.12 |
Referencias
- https://github.com/symfony/symfony/security/advisories/GHSA-ph86-p8f6-f9r2
- https://github.com/symfony/symfony/commit/ccb3f724c7ff55670a6fe3521c7bf1514cceb478
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-http/CVE-2026-45063.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45063.yaml
- https://github.com/symfony/symfony
- https://symfony.com/cve-2026-45063
- Vector CVSS
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N- Debilidad (CWE)
CWE-290- Plataforma
- Composer
- Paquete
symfony/security-http, symfony/symfony- Publicada
- 27.05.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-ph86-p8f6-f9r2 - CC BY 4.0
Historial de vulnerabilidades: symfony/symfony
Todas las vulnerabilidades publicadas de este paquete (Paquete de Composer), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 100
- Primera → última
- 11.2019 06.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 8
- Alta 28
- Media 51
- Baja 13
Divulgaciones por año
- 2019: 6
- 2020: 7
- 2021: 6
- 2022: 29
- 2023: 5
- 2024: 16
- 2025: 1
- 2026: 30
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