Prevent user enumeration using Guard or the new Authenticator-based Security
Description
The ability to enumerate users was possible without relevant permissions due to different exception messages depending on whether the user existed or not. It was also possible to enumerate users by using a timing attack, by comparing time elapsed when authenticating an existing user and authenticating a non-existing user.
Resolution
We now ensure that 403s are returned whether the user exists or not if the password is invalid or if the user does not exist.
The patch for this issue is available here for branch 3.4.
Credits
I would like to thank James Isaac and Mathias Brodala for reporting the issue and Robin Chalas for fixing the issue.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | lexik/jwt-authentication-bundle | >= 2.0.0, < 2.10.7, >= 2.11.0, < 2.11.3 | 2.10.7, 2.11.3 |
| Composer package | symfony/maker-bundle | >= 1.27.0, < 1.29.2, >= 1.30.0, < 1.31.1 | 1.29.2, 1.31.1 |
| Composer package | symfony/security | >= 5.0.0, < 5.2.8, >= 2.8.0, < 3.4.49, >= 4.0.0, < 4.4.24 | 5.2.8, 3.4.49, 4.4.24 |
| Composer package | symfony/security-core | >= 2.8.0, < 3.4.48, >= 4.0.0, < 4.4.23, >= 5.0.0, < 5.2.8 | 3.4.48, 4.4.23, 5.2.8 |
| Composer package | symfony/security-guard | >= 2.8.0, < 3.4.48, >= 4.0.0, < 4.4.23, >= 5.0.0, < 5.2.8 | 3.4.48, 4.4.23, 5.2.8 |
| Composer package | symfony/security-http | >= 5.1.0, < 5.2.8 | 5.2.8 |
| Composer package | symfony/symfony | >= 2.8.0, < 3.4.49, >= 4.0.0, < 4.4.24, >= 5.0.0, < 5.2.9 | 3.4.49, 4.4.24, 5.2.9 |
References
- https://github.com/symfony/symfony/security/advisories/GHSA-5pv8-ppvj-4h68
- https://nvd.nist.gov/vuln/detail/CVE-2021-21424
- https://github.com/symfony/symfony/commit/2a581d22cc621b33d5464ed65c4bc2057f72f011
- https://symfony.com/cve-2021-21424
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VRUS2H2SSOQWNLBD35SKIWIDQEMV2PD3
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UC7BND775DVZDQT3RMGD2HVB2PKLJDJW
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/RH7TMM5CHQYBFFGXWRPJDPB3SKCZXI2M
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KENRNLB3FYXYGDWRBH2PDBOZZKOD7VY4
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VRUS2H2SSOQWNLBD35SKIWIDQEMV2PD3
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UC7BND775DVZDQT3RMGD2HVB2PKLJDJW
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RH7TMM5CHQYBFFGXWRPJDPB3SKCZXI2M
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KENRNLB3FYXYGDWRBH2PDBOZZKOD7VY4
- https://lists.debian.org/debian-lts-announce/2023/07/msg00014.html
- https://github.com/symfony/symfony
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2021-21424.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security/CVE-2021-21424.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-http/CVE-2021-21424.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/security-guard/CVE-2021-21424.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/maker-bundle/CVE-2021-21424.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/lexik/jwt-authentication-bundle/CVE-2021-21424.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N- Weakness (CWE)
CWE-200, CWE-203- Platform
- Composer
- Package
lexik/jwt-authentication-bundle, symfony/maker-bundle, symfony/security- Disclosed
- 13.05.2021
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-5pv8-ppvj-4h68 - CC BY 4.0
Vulnerability history: symfony/security-guard
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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