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CVE-2021-21424

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

MEDIUM
5.3
CVSS Score
Published: May 13, 2021 at 12:00 AM UTC
Updated: June 17, 2026 at 03:35 AM UTC
3 products affected across 3 vendorsFedoraSymfonySymfony

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Severity
MEDIUM5.3
Exploit prediction
EPSS 2%

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Fedora· Fedora Projectrpm
95%
3334
Symfony· Sensiolabsdrupal
95%
2.8.0 ≤ v < 3.4.484.0.0 ≤ v < 4.4.235.0.0 ≤ v < 5.2.8
Affected range stops below 3.4.48, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.4.23, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.2.8, so it looks safe — our inference, not a vendor statement
Symfony· Symfonycomposer
60%
v < 3.4.48v < 4.4.23v < 5.2.8
Affected range stops below 3.4.48, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.4.23, so it looks safe — our inference, not a vendor statement
Affected range stops below 5.2.8, so it looks safe — our inference, not a vendor statement

References (7)

PatchThird Party Advisory
Source: [email protected]
https://github.com/symfony/symfony/commit/2a581d22cc621b33d5464ed65c4bc2057f72f011
PatchThird Party Advisory
Source: [email protected]
https://github.com/symfony/symfony/security/advisories/GHSA-5pv8-ppvj-4h68
Mailing List
Source: [email protected]
https://lists.debian.org/debian-lts-announce/2023/07/msg00014.html
Vendor Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KENRNLB3FYXYGDWRBH2PDBOZZKOD7VY4/
Vendor Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RH7TMM5CHQYBFFGXWRPJDPB3SKCZXI2M/
Vendor Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UC7BND775DVZDQT3RMGD2HVB2PKLJDJW/
Vendor Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VRUS2H2SSOQWNLBD35SKIWIDQEMV2PD3/

CVSS

5.3MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-200CWE-203

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