CVE-2021-21424 Prevent user enumeration using Guard or the new Authenticator-based Security
Attackers can enumerate valid usernames via inconsistent error responses in Symfony's user switching feature, exposing user existence information.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-21424?
CVE-2021-21424 is a medium-severity vulnerability in Fedoraproject Fedora, published on 13 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Symfony is a PHP framework for web and console applications and a set of reusable PHP components. The ability to enumerate users was possible without relevant permissions due to different handling depending on whether the user existed or not when attempting to use the switch users functionality. We now ensure that 403s are returned whether the user exists or not if a user cannot switch to a user or if the user does not exist. The patch for this issue is available for branch 3.4.
Which versions are affected by CVE-2021-21424?
35 open source packages ship an affected version, including symfony/security, symfony and lexik/jwt-authentication-bundle. It affects 2 products.
| Package | Affected | Fixed in |
|---|---|---|
symfony/security Packagist | From 2.8.0 | 3.4.49 |
symfony/security Packagist | From 2.8.0 | 3.4.49 |
symfony/security Packagist | From 4.0.0 | 4.4.24 |
symfony/security Packagist | From 4.0.0 | 4.4.24 |
symfony/security Packagist | From 5.0.0 | 5.2.8 |
symfony/security Packagist | From 5.0.0 | 5.2.8 |
29 more packages
symfony Bitnami | From 2.8.0 | 3.4.48, 4.4.23, 5.2.8 |
lexik/jwt-authentication-bundle Packagist | From 2.0.0 | 2.10.7 |
lexik/jwt-authentication-bundle Packagist | From 2.0.0 | 2.10.7 |
lexik/jwt-authentication-bundle Packagist | From 2.11.0 | 2.11.3 |
lexik/jwt-authentication-bundle Packagist | From 2.11.0 | 2.11.3 |
symfony/maker-bundle Packagist | From 1.27.0 | 1.29.2 |
symfony/maker-bundle Packagist | From 1.27.0 | 1.29.2 |
symfony/maker-bundle Packagist | From 1.30.0 | 1.31.1 |
symfony/maker-bundle Packagist | From 1.30.0 | 1.31.1 |
symfony/security-core Packagist | From 2.8.0 | 3.4.48 |
symfony/security-core Packagist | From 2.8.0 | 3.4.48 |
symfony/security-core Packagist | From 4.0.0 | 4.4.23 |
symfony/security-core Packagist | From 4.0.0 | 4.4.23 |
symfony/security-core Packagist | From 5.0.0 | 5.2.8 |
symfony/security-core Packagist | From 5.0.0 | 5.2.8 |
symfony/security-guard Packagist | From 2.8.0 | 3.4.48 |
symfony/security-guard Packagist | From 2.8.0 | 3.4.48 |
symfony/security-guard Packagist | From 4.0.0 | 4.4.23 |
symfony/security-guard Packagist | From 4.0.0 | 4.4.23 |
symfony/security-guard Packagist | From 5.0.0 | 5.2.8 |
symfony/security-guard Packagist | From 5.0.0 | 5.2.8 |
symfony/security-http Packagist | From 5.1.0 | 5.2.8 |
symfony/security-http Packagist | From 5.1.0 | 5.2.8 |
symfony/symfony Packagist | From 2.8.0 | 3.4.49 |
symfony/symfony Packagist | From 2.8.0 | 3.4.49 |
symfony/symfony Packagist | From 4.0.0 | 4.4.24 |
symfony/symfony Packagist | From 4.0.0 | 4.4.24 |
symfony/symfony Packagist | From 5.0.0 | 5.2.9 |
symfony/symfony Packagist | From 5.0.0 | 5.2.9 |
Products include Fedoraproject Fedora, Sensiolabs Symfony.
How do I fix CVE-2021-21424?
Upgrade symfony/security to a fixed version for your release line: 3.4.49, 4.4.24 or 5.2.8.
Is CVE-2021-21424 being exploited?
There is no known exploitation of CVE-2021-21424 in the wild and no public exploit code.
Public exploit code: 2 proofs of concept on GitHub.
Other vulnerabilities in Fedoraproject Fedora
Sources
Also known as BIT-symfony-2021-21424, DEBIAN-CVE-2021-21424, GHSA-5pv8-ppvj-4h68, UBUNTU-CVE-2021-21424.