CVE-2020-27838: Keycloak core Keycloak Discloses Information Without Authentication Vulnerability

MODERATE
Advisory Identifier: GHSA-pcv5-m2wh-66j3
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CVSS 6.5
CWE-287
Published
Advisory Summary

CVE-2020-27838 is a MODERATE (CVSS 6.5) keycloak discloses information without authentication vulnerability (CWE-287: Improper Authentication) affecting Keycloak core libraries in the Maven ecosystem. The issue involves keycloak discloses information without authentication. Remediation is available by upgrading affected packages to version 13.0.0.

CVE-2020-27838 at a Glance

CVE Identifier CVE-2020-27838
GHSA Identifier GHSA-pcv5-m2wh-66j3
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-287: Improper Authentication
Affected Product Keycloak core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 6.5

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

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

How to Fix CVE-2020-27838

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: 13.0.0 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-core</artifactId>
    <version>13.0.0</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-2020-27838, 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 13.0.0), 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-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. 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 in versions prior to 13.0.0. The client registration endpoint allows fetching information about PUBLIC clients (like client secret) without authentication which could be an issue if the same PUBLIC client changed to CONFIDENTIAL later. The highest threat from this vulnerability is to data confidentiality.

CVE-2020-27838 Affected Keycloak core Versions

1 component(s)
Fixed Versions:
13.0.0
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-core
maven/org.keycloak/keycloak-core
Maven
< 13.0.0
13.0.0

References

NVD — CVE-2020-27838 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-27838
Keycloak core Source Repository REPOSITORY
https://github.com/keycloak/keycloak/pull/7790
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/9356843c6c3d7097d010b3bb6f91e25fcaba378c
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=1906797

Frequently Asked Questions

What is CVE-2020-27838?
CVE-2020-27838 is a security vulnerability in Keycloak core involving Keycloak discloses information without authentication under CWE-287: Improper Authentication.
Which Keycloak core versions are affected?
Affected versions include releases prior to 13.0.0 across affected packages: org.keycloak:keycloak-core.
What version fixes CVE-2020-27838?
Upgrading to 13.0.0 (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 13.0.0. Upgrade your dependency to 13.0.0 or later.
What is the CVSS score of CVE-2020-27838?
CVE-2020-27838 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2020-27838?
CVE-2020-27838 is classified under CWE-287: Improper Authentication (When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.).
How can I check Maven dependencies for CVE-2020-27838?
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-pcv5-m2wh-66j3",
  "modified" : "2024-04-22T23:11:37Z",
  "published" : "2022-05-24T17:43:50Z",
  "aliases" : [ "CVE-2020-27838" ],
  "summary" : "Keycloak discloses information without authentication",
  "details" : "A flaw was found in keycloak in versions prior to 13.0.0. The client registration endpoint allows fetching information about PUBLIC clients (like client secret) without authentication which could be an issue if the same PUBLIC client changed to CONFIDENTIAL later. The highest threat from this vulnerability is to data confidentiality.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "13.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-27838"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/pull/7790"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/9356843c6c3d7097d010b3bb6f91e25fcaba378c"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1906797"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-04-22T23:11:37Z",
    "nvd_published_at" : "2021-03-08T22:15:00Z"
  }
}