CVE-2026-123746 Symfony: Programmatic Logins Skip the checkPostAuth() Method of User Checkers
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-123746?
CVE-2026-123746 is a low-severity vulnerability in sensiolabs symfony, published on 6 Nov 2026.
Official description
The Symfony Security HTTP component AuthenticatorManager::authenticateUser() does not run the firewall user checker’s checkPostAuth() method when a user is authenticated programmatically, allowing an account rejected by a custom user checker, such as an expired account, to be authenticated in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.
AuthenticatorManager::authenticateUser() is used by UserAuthenticatorInterface::authenticateUser() and by the SecurityBundle’s Security::login() to authenticate a user programmatically, but it does not dispatch the security.authentication.success event, on which checkPostAuth() runs. The fix for CVE-2024-50341 made Security::login() call checkPreAuth(), but checkPostAuth() was still skipped. As a result, an account rejected by a custom user checker in checkPostAuth() is refused by form login and the other authenticators of the firewall, but can still be authenticated programmatically.
Applications are affected when they use a custom user checker that rejects users in checkPostAuth() and authenticate users programmatically, for example after a password reset or an e-mail verification link. A user whose account is rejected can then obtain an authenticated session through that flow. The default user checker does nothing in checkPostAuth(), so the default configuration is not affected.
The fix makes AuthenticatorManager::authenticateUser() dispatch the security.authentication.success event once the token is created and before it is stored, as authentications through the firewall do, so that checkPostAuth() runs and can reject the user.
Weakness: CWE-288
Which versions are affected by CVE-2026-123746?
How do I fix CVE-2026-123746?
Upgrade to a fixed version.
Is CVE-2026-123746 being exploited?
There is no known exploitation of CVE-2026-123746 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-123746, GHSA-8f57-m8wj-x65w, UBUNTU-CVE-2026-123746.