CVE-2021-21424: Fedoraproject Fedora

Medium severity, CVSS 5.3. EPSS: 1.7% chance of exploitation in the next 30 days.

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.

Affected products

• Fedoraproject Fedora: version 33 only; version 34 only
• Sensiolabs Symfony: from 2.8.0, before 3.4.48 (fixed in 3.4.48); from 4.0.0, before 4.4.23 (fixed in 4.4.23); from 5.0.0, before 5.2.8 (fixed in 5.2.8)

Published 2021-05-13. Last modified 2026-06-17.