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OpenAdvisories
Medium · 5.3 Public exploit CVE-2021-21424 BIT-symfony-2021-21424EUVD-2021-0960GHSA-5pv8-ppvj-4h68

Prevent user enumeration using Guard or the new Authenticator-based Security

Published May 13, 2021 · Updated Aug 3, 2024 · Assigned by GitHub_M

Vendor: symfony Product: symfony Package: lexik/jwt-authentication-bundle Package: symfony Package: symfony Package: symfony/maker-bundle Package: symfony/security Package: symfony/security-core Package: symfony/security-guard Package: symfony/security-http Package: symfony/symfony Ecosystem: Debian Ecosystem: Packagist Ecosystem: Ubuntu

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.

Affected products

VendorProductAffectedFixed
symfony symfony >= 2.8.0, < 3.4.48, >= 4.0.0, < 4.4.23, >= 5.0.0, < 5.2.8 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

Debian

Security tracker ↗
ReleasePackageFixed inAdvisory
Debian 14 symfony 4.4.19+dfsg-2 —
Debian 13 symfony 4.4.19+dfsg-2 —
Debian 12 symfony 4.4.19+dfsg-2 —
Debian 10 symfony 3.4.22+dfsg-2+deb10u2 DLA-3493-1

Ubuntu

Security tracker ↗
ReleasePackageFixed inAdvisory
Ubuntu Pro 20.04 LTS symfony 4.3.8+dfsg-1ubuntu1+esm1 USN-5290-1
Ubuntu Pro 18.04 LTS symfony 3.4.6+dfsg-1ubuntu0.1+esm2 USN-5290-1

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

GitHub 2 repositories

  • moften/Symfony-CVE-Scanner-PoC- ★ 0 · May 7, 2025

    CVE-2021-21424 - CRLF Injection - CVE-2021-41268 - Host Header Injection - CVE-2022-24894 - WebProfiler abierto - CVE-2019-10909 - Directory Traversal

  • moften/CVE-2021-21424 ★ 0 · Apr 14, 2025

    El WebProfiler de Symfony expone rutas internas del servidor si no está deshabilitado en producción

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

Affected packages

EcosystemPackageAffectedFixedRecord
Packagist lexik/jwt-authentication-bundle >= 2.0.0, < 2.10.7 2.10.7 GHSA-5pv8-ppvj-4h68
Packagist lexik/jwt-authentication-bundle >= 2.11.0, < 2.11.3 2.11.3 GHSA-5pv8-ppvj-4h68
Packagist symfony/maker-bundle >= 1.27.0, < 1.29.2 1.29.2 GHSA-5pv8-ppvj-4h68
Packagist symfony/maker-bundle >= 1.30.0, < 1.31.1 1.31.1 GHSA-5pv8-ppvj-4h68
Packagist symfony/security >= 5.0.0, < 5.2.8 5.2.8 GHSA-5pv8-ppvj-4h68
Packagist symfony/security >= 2.8.0, < 3.4.49 3.4.49 GHSA-5pv8-ppvj-4h68
Packagist symfony/security >= 4.0.0, < 4.4.24 4.4.24 GHSA-5pv8-ppvj-4h68
Packagist symfony/security-core >= 2.8.0, < 3.4.48 3.4.48 GHSA-5pv8-ppvj-4h68
Packagist symfony/security-core >= 4.0.0, < 4.4.23 4.4.23 GHSA-5pv8-ppvj-4h68
Packagist symfony/security-core >= 5.0.0, < 5.2.8 5.2.8 GHSA-5pv8-ppvj-4h68
Packagist symfony/security-guard >= 2.8.0, < 3.4.48 3.4.48 GHSA-5pv8-ppvj-4h68
Packagist symfony/security-guard >= 4.0.0, < 4.4.23 4.4.23 GHSA-5pv8-ppvj-4h68
Packagist symfony/security-guard >= 5.0.0, < 5.2.8 5.2.8 GHSA-5pv8-ppvj-4h68
Packagist symfony/security-http >= 5.1.0, < 5.2.8 5.2.8 GHSA-5pv8-ppvj-4h68
Packagist symfony/symfony >= 2.8.0, < 3.4.49 3.4.49 GHSA-5pv8-ppvj-4h68
Packagist symfony/symfony >= 4.0.0, < 4.4.24 4.4.24 GHSA-5pv8-ppvj-4h68
Packagist symfony/symfony >= 5.0.0, < 5.2.9 5.2.9 GHSA-5pv8-ppvj-4h68

Advisories 2

References