What is the CVSS score of CVE-2021-21424?

CVE-2021-21424 has a CVSS 3.1 base score of 5.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N. EPSS exploitation probability: 1.7%.

Is there a patch available for CVE-2021-21424?

Yes, a patch is available for CVE-2021-21424. Update the affected software to the latest version immediately.

Symfony CVE-2021-21424

MEDIUM

Information Exposure (CWE-200)

2021-05-13 security-advisories@github.com

PHP Information Disclosure Fedora Symfony Sensiolabs Fedoraproject

5.3

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-200 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V14 - Data Protection Data exposure prevention MITRE ATT&CK 2 techniques across 2 tactics: Collection, Discovery The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 5.3 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	A remote attacker could access sensitive data that should not be disclosed by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Patch available 1.7% exploitation probability (EPSS)

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AnalysisAI

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Exposure of Sensitive Information vulnerability could allow attackers to access sensitive data that should not be disclosed.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Minimize information in error messages, implement proper access controls, encrypt sensitive data at rest and in transit.

Affected Packages

composer lexik/jwt-authentication-bundle fix: 2.10.7, 2.11.3

composer symfony/maker-bundle fix: 1.29.2, 1.31.1

composer symfony/security fix: 3.4.49, 4.4.24, 5.2.8

composer symfony/security-core fix: 3.4.48, 4.4.23, 5.2.8

composer symfony/security-guard fix: 3.4.48, 4.4.23, 5.2.8

composer symfony/security-http fix: 5.2.8

composer symfony/symfony fix: 3.4.49, 4.4.24, 5.2.9

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 7 packages in composer

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Exposure of Sensitive Information (CWE-200), which allows attackers to access sensitive data that should not be disclosed. 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 include: Sensiolabs Symfony, Fedoraproject Fedora.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 5.3 MEDIUM

AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

DescriptionNVD

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.

Threat Intelligence Overview

EPSS Score

1.7%

Top 25% exploitable

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC No

EPSS 1.7%

Patch available Yes

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +2

CVSS: +26

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.