CVE-2024-51996 is a high-severity (CVSS 7.5) Improper Authentication vulnerability in symfony/security-http. A fix is available for symfony/security-http — see the affected versions and patch details below.
Symphony has an Authentication Bypass via RememberMe
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-51996.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
symfony/security-http🐘symfony/security-http🐘symfony/security-httpReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Description
When consuming a persisted remember-me cookie, Symfony does not check if the username persisted in the database matches the username attached with the cookie, leading to authentication bypass.
Resolution
The PersistentRememberMeHandler class now ensures the submitted username is the cookie owner.
The patch for this issue is available here for branch 5.4.
Credits
We would like to thank Moritz Rauch - Pentryx AG for reporting the issue and Jérémy Derussé for providing the fix.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | symfony/security-http | ≥ 5.3.0&&< 5.4.47 | 5.4.47composer require symfony/security-http:^5.4.47 |
| 🐘Packagist | symfony/security-http | ≥ 6.0.0-BETA1&&< 6.4.15 | 6.4.15composer require symfony/security-http:^6.4.15 |
| 🐘Packagist | symfony/security-http | ≥ 7.0.0-BETA1&&< 7.1.8 | 7.1.8composer require symfony/security-http:^7.1.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/security-http, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update symfony/security-http to 5.4.47 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-51996 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2024-51996 in your dependencies?
Find it across Packagist, including transitive dependencies.