Symfony X509 Login: Crafted Certificate Names Can Log In as Another User

Published as "CVE-2026-118513: X509Authenticator and X509AuthenticationListener Read Escaped RFC 2253 Commas and Bare Slashes Inside a DN Value as RDN Boundaries: Incomplete Fix for CVE-2026-45063"

high Symfony Symfony components · Last reviewed Nov 6, 2026

CVE: CVE-2026-118513
GHSA: None
Packagist: PKSA-k1xt-28gt-fw9y
Reported: Nov 4, 2026

Lets a client certificate holder log in as another user's email address in apps that use Symfony's X509 authenticator.

Affected and fixed versions

In 2 packages: symfony/security-http and symfony/symfony. Find the row for the version you run, and update to the release next to it.

If you run	Update to	Support
8.1.0 – 8.1.10	8.1.11	Supported
7.4.0 – 7.4.22	7.4.23	Supported
6.4.0 – 6.4.49	6.4.50	Supported
5.4.0 – 5.4.55	5.4.56	Supported

Show 16 older branches, no longer supported

8.0.0 – 8.0.x	8.1.11
7.0.0 – 7.0.x	7.4.23
7.1.0 – 7.1.x	7.4.23
7.2.0 – 7.2.x	7.4.23
7.3.0 – 7.3.x	7.4.23
6.0.0 – 6.0.x	6.4.50
6.1.0 – 6.1.x	6.4.50
6.2.0 – 6.2.x	6.4.50
6.3.0 – 6.3.x	6.4.50
2.0.0 – 2.x	5.4.56
3.0.0 – 3.x	5.4.56
4.0.0 – 4.x	5.4.56
5.0.0 – 5.0.x	5.4.56
5.1.0 – 5.1.x	5.4.56
5.2.0 – 5.2.x	5.4.56
5.3.0 – 5.3.x	5.4.56

Upgrade

Run the line for the branch you are on. 1 other package listed above is affected too; update it the same way.

composer require symfony/security-http:^8.1.11
composer require symfony/security-http:^7.4.23
composer require symfony/security-http:^6.4.50
composer require symfony/security-http:^5.4.56

What this means

Someone holding a client certificate from a CA your app trusts can log in as another user, including an admin. They need to be able to choose text in the certificate's name fields. Symfony's X509 login read the user's email from the certificate's subject name, and crafted text inside one field could pass as another user's email.

This is an incomplete fix for CVE-2026-45063.

Who is affected

Apps on symfony/security-http (also part of symfony/symfony) that log users in with client certificates through X509Authenticator, the x509 firewall option. On 5.4, the older X509AuthenticationListener is affected too, and it was never covered by the first fix.

The Symfony advisory says you're safe if your firewall reads a single attribute as the user key, such as Apache's SSL_CLIENT_S_DN_Email. You're also safe if your CA builds or checks the subject itself instead of accepting what the requester asks for. The nginx setup in Symfony's docs is exposed, because nginx has no per-attribute value.

What to do

Update to 5.4.56, 6.4.50, 7.4.23 or 8.1.11. If you're on 8.0, update to 8.1.11. The fix (5.4, 6.4) splits the subject into its parts before looking for the email.

Symfony also says some formats can't be read safely at all: Apache's LegacyDNStringFormat and nginx's $ssl_client_s_dn_legacy with OpenSSL older than 3.0, and HAProxy's ssl_c_s_dn. Switch those to the RFC 2253 format or to a per-attribute value.

Reported by Oryam Halachmi, dahmani toumi and Stapat.

Check your app with an agent

Paste this into a coding agent that can read your project, such as Claude Code, Codex or Amp. It checks your composer.lock against the versions above and tells you what to update, without changing anything.

Check whether the PHP project you have access to is affected by this security advisory, and tell me what to update. Do a read-only check: don't edit files, don't run composer update or composer require, and don't try to reproduce the flaw.

Advisory: Symfony X509 Login: Crafted Certificate Names Can Log In as Another User (CVE-2026-118513)
Details: https://phpnews.net/security/symfony/cve-2026-118513

Affected versions, as Composer constraints:
- symfony/security-http, symfony/symfony: >=2.0.0,<3.0.0|>=3.0.0,<4.0.0|>=4.0.0,<5.0.0|>=5.0.0,<5.1.0|>=5.1.0,<5.2.0|>=5.2.0,<5.3.0|>=5.3.0,<5.4.0|>=5.4.0,<5.4.56|>=6.0.0,<6.1.0|>=6.1.0,<6.2.0|>=6.2.0,<6.3.0|>=6.3.0,<6.4.0|>=6.4.0,<6.4.50|>=7.0.0,<7.1.0|>=7.1.0,<7.2.0|>=7.2.0,<7.3.0|>=7.3.0,<7.4.0|>=7.4.0,<7.4.23|>=8.0.0,<8.1.0|>=8.1.0,<8.1.11

Fixed releases on branches that still get security fixes:
- 8.1.0 – 8.1.10: update to 8.1.11
- 7.4.0 – 7.4.22: update to 7.4.23
- 6.4.0 – 6.4.49: update to 6.4.50
- 5.4.0 – 5.4.55: update to 5.4.56

1. Find every composer.lock in the project outside vendor/ (a monorepo can have one per app) and read the installed version of each package above. Packages installed as dependencies of other packages count too.
2. Compare each installed version with its constraint: "|" separates alternative ranges, and "," means both bounds apply.
3. For each affected install, read "What this means" at https://phpnews.net/security/symfony/cve-2026-118513 and check whether the project meets the conditions it describes (a feature in use, a config value, a driver). Say which conditions you could check and which you couldn't.
4. Report a table: lock file | package | installed version | affected (yes, no or unknown) | conditions met (yes, no or unknown) | update to | evidence. For each affected package, give the command that would fix it, without running it: composer update <package> --with-dependencies when it is only installed as a dependency of another package, or composer require with the fixed version when composer.json requires it directly. If the installed version is on a branch with no fixed release listed, say it needs a move to a newer branch.

Sources

← All Symfony advisories