CVE-2021-3754: Keycloak services Keycloak's Improper Input Validation Allows Vulnerability

LOW
Advisory Identifier: GHSA-4vc8-pg5c-vg4x
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CVSS 3.7
CWE-670
Published
Advisory Summary

CVE-2021-3754 is a LOW (CVSS 3.7) keycloak's improper input validation allows vulnerability (CWE-670: Always-Incorrect Control Flow Implementation) affecting Keycloak services libraries in the Maven ecosystem. The issue involves keycloak's improper input validation allows using email as username. Remediation is available by upgrading affected packages to version 24.0.1.

CVE-2021-3754 at a Glance

CVE Identifier CVE-2021-3754
GHSA Identifier GHSA-4vc8-pg5c-vg4x
Severity LOW
CVSS v3.1 Base Score 3.7
CWE Classification CWE-670: Always-Incorrect Control Flow Implementation
Affected Product Keycloak services
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 3.7

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability Low (A:L)

How to Fix CVE-2021-3754

To remediate this vulnerability, upgrade all affected Keycloak services dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.keycloak:keycloak-services fixed: 24.0.1 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-services</artifactId>
    <version>24.0.1</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.keycloak

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-3754, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.keycloak

Analyze the terminal output to locate any version of Keycloak services in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 24.0.1), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.keycloak command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-670: Always-Incorrect Control Flow Implementation, where the code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated. In Keycloak services, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Keycloak allows the use of email as a username and doesn't check that an account with this email already exists. That could lead to the unability to reset/login with email for the user. This is caused by usernames being evaluated before emails.

CVE-2021-3754 Affected Keycloak services Versions

1 component(s)
Fixed Versions:
24.0.1
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-services
maven/org.keycloak/keycloak-services
Maven
< 24.0.1
24.0.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/keycloak/keycloak/security/advisories/GHSA-4vc8-pg5c-vg4x
NVD — CVE-2021-3754 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-3754
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/f9708037383aa98741e4850447de64dc4a0d4b4e
Keycloak services Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2021-3754
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=1999196
Keycloak services Source Repository REPOSITORY
https://github.com/keycloak/keycloak

Frequently Asked Questions

What is CVE-2021-3754?
CVE-2021-3754 is a security vulnerability in Keycloak services involving Keycloak's improper input validation allows using email as username under CWE-670: Always-Incorrect Control Flow Implementation.
Which Keycloak services versions are affected?
Affected versions include releases prior to 24.0.1 across affected packages: org.keycloak:keycloak-services.
What version fixes CVE-2021-3754?
Upgrading to 24.0.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-services affected?
Yes, org.keycloak:keycloak-services is affected in releases prior to 24.0.1. Upgrade your dependency to 24.0.1 or later.
What is the CVSS score of CVE-2021-3754?
CVE-2021-3754 has a CVSS v3.1 base score of 3.7 (LOW) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2021-3754?
CVE-2021-3754 is classified under CWE-670: Always-Incorrect Control Flow Implementation (The code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated.).
How can I check Maven dependencies for CVE-2021-3754?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.keycloak'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4vc8-pg5c-vg4x",
  "modified" : "2024-12-20T17:49:09Z",
  "published" : "2024-06-12T19:41:05Z",
  "aliases" : [ "CVE-2021-3754" ],
  "summary" : "Keycloak's improper input validation allows using email as username",
  "details" : "Keycloak allows the use of email as a username and doesn't check that an account with this email already exists. That could lead to the unability to reset/login with email for the user. This is caused by usernames being evaluated before emails.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-services"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "24.0.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/security/advisories/GHSA-4vc8-pg5c-vg4x"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-3754"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/f9708037383aa98741e4850447de64dc4a0d4b4e"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2021-3754"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1999196"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-670" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-06-12T19:41:05Z",
    "nvd_published_at" : null
  }
}