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🛡️ CVE-2026-45063 — symfony

🔴 CVSS 9.1 — Critical ✅ No Known Exploit CWE-290 NVD
9.1
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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,[email protected]) 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](https://github.com/symfony/symfony/commit/ccb3f724c7ff55670a6fe3521c7bf1514cceb478) for branch 5.4.

Credits

Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

CVE-2026-45063 is classified as CWE-290: Authentication Bypass by Spoofing. Identity is inferred from something an attacker can forge, such as a header or address.

Affected software

CVE-2026-45063 is recorded against 3 packages.

  • symfony (from 8.0.0 up to 8.0.12)
  • symfony/security-http (from 8.0.0-BETA1 up to 8.0.12)
  • symfony/symfony (from 8.0.0-BETA1 up to 8.0.12)

Timeline and source

Published on 14 July 2026 and last revised on 15 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com
github.com
github.com
github.com
github.com

Other advisories for this package

symfony has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-290: Authentication Bypass by Spoofing) in other software:

CVE-2026-45063 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity CRITICAL
CVSS Score 9.1
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CWE CWE-290
Public Exploit ✅ No
Source NVD
Published 2026-07-14
Updated 2026-08-20
Modified 2026-07-15

Affected Packages

Software From version Fixed in
symfony 8.0.0 8.0.12
symfony/security-http 8.0.0-BETA1 8.0.12
symfony/symfony 8.0.0-BETA1 8.0.12

Similar Threats

Exploit Protection

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