Symfony possible session fixation vulnerability
Description
SessionStrategyListener does not always migrate the session after a successful login. It only migrate the session when the logged-in user identifier changes. In some use cases, the user identifier doesn't change between the verification phase and the successful login, while the token itself changes from one type (partially-authenticated) to another (fully-authenticated). When this happens, the session id should be regenerated to prevent possible session fixations.
Resolution
Symfony now checks the type of the token in addition to the user identifier before deciding whether the session id should be regenerated.
The patch for this issue is available here for branch 5.4.
Credits
We would like to thank Robert Meijers for reporting the issue and providing the fix.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | symfony/security-http | >= 5.4.21, < 5.4.31, >= 6.2.7, < 6.3.8 | 5.4.31, 6.3.8 |
| Composer package | symfony/symfony | >= 5.4.21, < 5.4.31, >= 6.2.7, < 6.3.8 | 5.4.31, 6.3.8 |
References
- https://github.com/symfony/symfony/security/advisories/GHSA-m2wj-r6g3-fxfx
- https://nvd.nist.gov/vuln/detail/CVE-2023-46733
- https://github.com/symfony/symfony/commit/7467bd7e3f888b333102bc664b5e02ef1e7f88b9
- https://github.com/symfony/symfony/commit/dc356499d5ceb86f7cf2b4c7f032eca97061ed74
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2023-46733.yaml
- https://github.com/symfony/symfony
- https://symfony.com/cve-2023-46733
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N- Weakness (CWE)
CWE-384- Platform
- Composer
- Package
symfony/security-http, symfony/symfony- Disclosed
- 12.11.2023
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-m2wj-r6g3-fxfx - CC BY 4.0
Vulnerability history: symfony/symfony
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 100
- First → latest
- 11.2019 06.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 8
- High 28
- Medium 51
- Low 13
Disclosures per year
- 2019: 6
- 2020: 7
- 2021: 6
- 2022: 29
- 2023: 5
- 2024: 16
- 2025: 1
- 2026: 30
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Symfony possible session fixation vulnerability this entry
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