CVE-2020-27826: Keycloak core Authentication Bypass Vulnerability

HIGH
Advisory Identifier: GHSA-m9cj-v55f-8x26
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CVSS 8.8
CWE-250
Published
Advisory Summary

CVE-2020-27826 is a HIGH (CVSS 8.8) authentication bypass vulnerability (CWE-250: Execution with Unnecessary Privileges) affecting Keycloak core libraries in the Maven ecosystem. The issue involves authentication bypass in keycloak. Remediation is available by upgrading affected packages to version 12.0.0.

CVE-2020-27826 at a Glance

CVE Identifier CVE-2020-27826
GHSA Identifier GHSA-m9cj-v55f-8x26
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-250: Execution with Unnecessary Privileges
Affected Product Keycloak core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.8

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

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

How to Fix CVE-2020-27826

To remediate this vulnerability, upgrade all affected Keycloak core 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-core fixed: 12.0.0 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-core</artifactId>
    <version>12.0.0</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-2020-27826, 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 core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 12.0.0), 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-250: Execution with Unnecessary Privileges, where the product performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses. In Keycloak core, 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

A flaw was found in Keycloak before version 12.0.0 where it is possible to update the user's metadata attributes using Account REST API. This flaw allows an attacker to change its own NameID attribute to impersonate the admin user for any particular application.

CVE-2020-27826 Affected Keycloak core Versions

1 component(s)
Fixed Versions:
12.0.0
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-core
maven/org.keycloak/keycloak-core
Maven
< 12.0.0
12.0.0

References

NVD — CVE-2020-27826 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-27826
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/dae4a3eaf26590b8d441b8e4bec3b700ee303b72
Keycloak core Security Information SECURITY
https://access.redhat.com/security/cve/cve-2020-27826
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=1905089

Frequently Asked Questions

What is CVE-2020-27826?
CVE-2020-27826 is a security vulnerability in Keycloak core involving Authentication Bypass in keycloak under CWE-250: Execution with Unnecessary Privileges.
Which Keycloak core versions are affected?
Affected versions include releases prior to 12.0.0 across affected packages: org.keycloak:keycloak-core.
What version fixes CVE-2020-27826?
Upgrading to 12.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-core affected?
Yes, org.keycloak:keycloak-core is affected in releases prior to 12.0.0. Upgrade your dependency to 12.0.0 or later.
What is the CVSS score of CVE-2020-27826?
CVE-2020-27826 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2020-27826?
CVE-2020-27826 is classified under CWE-250: Execution with Unnecessary Privileges (The product performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses.).
How can I check Maven dependencies for CVE-2020-27826?
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-m9cj-v55f-8x26",
  "modified" : "2022-03-18T17:55:26Z",
  "published" : "2022-03-18T17:55:26Z",
  "aliases" : [ "CVE-2020-27826" ],
  "summary" : "Authentication Bypass in keycloak",
  "details" : "A flaw was found in Keycloak before version 12.0.0 where it is possible to update the user's metadata attributes using Account REST API. This flaw allows an attacker to change its own NameID attribute to impersonate the admin user for any particular application.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "12.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-27826"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/dae4a3eaf26590b8d441b8e4bec3b700ee303b72"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/cve-2020-27826"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1905089"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-250" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-06-01T18:10:09Z",
    "nvd_published_at" : "2021-05-28T11:15:00Z"
  }
}