CVE-2024-51996

What it actually does

Authentication bypass in remember-me cookie handling where the persisted username in the database is not validated against the username in the cookie before granting access.

Why it matters to the business

Attackers can gain unauthorized access to user accounts across Symfony-based applications, increasing risk of data exposure or account takeover in environments using remember-me functionality.

How an attack unfolds

An attacker obtains or crafts a remember-me cookie containing a username, submits it to the application, and the missing username match check allows authentication as a different user than the one stored in the database.

How to fix it

Upgrade Symfony to version 5.4.47, 6.4.15, or 7.1.8. Apply the fix from commit d869cc180cf38d3848feff1dcf38fefaecfd8177 in the symfony/symfony repository.

How to confirm the fix worked

Verify the installed Symfony version matches a fixed release, review authentication configuration for remember-me usage, and test cookie consumption with mismatched usernames in a staging environment.

Typical attack path

1. Obtain or craft a remember-me cookie with a target username
2. Submit the cookie to the Symfony application's authentication endpoint
3. Bypass normal username validation due to missing database match check
4. Gain authenticated session as the target user

How to detect it

Review application authentication logs for remember-me cookie usage, correlate with database user records for mismatches, and inspect session creation events around the time of potential exploitation.

What your security team should do

• Prioritize upgrade to a fixed Symfony version in all affected applications
• Audit remember-me cookie usage and consider disabling the feature if not required
• Monitor authentication logs for anomalous login patterns after patching