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High

Symfony Vulnerable to Identity Spoofing via Unanchored DN Regex in X509Authenticator

  • Disclosed: 27.05.2026
  • Updated: 11.10.2026 10:22

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.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Composer package 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
Composer package 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

References

CVSS score -
CVSS vector
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
Weakness (CWE)
CWE-290
Platform
Composer
Package
symfony/security-http, symfony/symfony
Disclosed
27.05.2026
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-ph86-p8f6-f9r2 - CC BY 4.0

Vulnerability history: symfony/security-http

All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (20) in the archive
Total entries
20
First → latest
12.2019 06.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • High 10
  • Medium 8
  • Low 2

Disclosures per year

Severity:
  1. Symfony: Security Firewall Bypass via failure_forward Subrequest: Unauthenticated Access to access_control-Protected GET Routes
    High CVE-2026-48489 < 5.4.53, >= 6.0.0, < 6.4.41, >= 7.0.0, < 7.4.13, >= 8.0.0, < 8.0.13 5.4.53, 6.4.41, 7.4.13, 8.0.13
  2. Symfony's HEAD Request Bypasses methods: ['GET'] Filter in #[IsGranted] / #[IsSignatureValid] / #[IsCsrfTokenValid]
    High CVE-2026-45075 >= 7.4.0, < 7.4.12, >= 8.0.0, < 8.0.12 7.4.12, 8.0.12
  3. Symfony Vulnerable to Identity Spoofing via Unanchored DN Regex in X509Authenticator this entry
    High CVE-2026-45063 < 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
  4. Symfony has an Authentication Bypass via RememberMe
    High · 7.5 CVE-2024-51996 >= 5.3.0, < 5.4.47, >= 6.0.0-BETA1, < 6.4.15, >= 7.0.0-BETA1, < 7.1.8 5.4.47, 6.4.15, 7.1.8
  5. Symphony Denial of Service Via Overlong Usernames
    High · 7.5 CVE-2016-4423 >= 2.3.0, < 2.3.41, >= 2.4.0, < 2.7.13, >= 2.8.0, < 2.8.6, >= 3.0.0, < 3.0.6 2.3.41, 2.7.13, 2.8.6, 3.0.6
  6. Symfony Vulnerable to Timing Attack
    High CVE-2015-8125 >= 2.4.0, < 2.6.12, >= 2.7.0, < 2.7.7 2.6.12, 2.7.7
  7. Symfony Session Fixation Vulnerability
    High · 8.1 CVE-2018-11385 >= 2.7.0, < 2.7.48, >= 2.8.0, < 2.8.41, >= 3.0.0, < 3.3.17, >= 3.4.0, < 3.4.11, >= 4.0.0, < 4.0.11 2.7.48, 2.8.41, 3.3.17, 3.4.11, 4.0.11
  8. Symfony CSRF Token Fixation
    High · 8.8 CVE-2018-11406 >= 2.7.0, < 2.7.48, >= 2.8.0, < 2.8.41, >= 3.0.0, < 3.3.17, >= 3.4.0, < 3.4.11, >= 4.0.0, < 4.0.11 2.7.48, 2.8.41, 3.3.17, 3.4.11, 4.0.11
  9. Firewall configured with unanimous strategy was not actually unanimous in Symfony
    High · 7.6 CVE-2020-5275 >= 4.4.0, < 4.4.7, >= 5.0.0, < 5.0.7 4.4.7, 5.0.7
  10. Improper authentication in Symfony
    High · 7.5 CVE-2019-10911 >= 2.7.0, < 2.7.51, >= 2.8.0, < 2.8.50, >= 3.0.0, < 3.4.26, >= 4.0.0, < 4.1.12, >= 4.2.0, < 4.2.7 2.7.51, 2.8.50, 3.4.26, 4.1.12, 4.2.7

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