CVE-2026-37979: Keycloak Information Disclosure Vulnerability

MODERATE
Advisory Identifier: GHSA-4x37-hw65-52w8
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CVSS 6.5
CWE-284
Published
Advisory Summary

CVE-2026-37979 is a MODERATE (CVSS 6.5) information disclosure vulnerability (CWE-284: Improper Access Control) affecting Keycloak libraries in the Maven ecosystem. The issue involves information disclosure via oidc token introspection endpoint audience bypass. Remediation is available by upgrading affected packages to version 26.6.2.

CVE-2026-37979 at a Glance

CVE Identifier CVE-2026-37979
GHSA Identifier GHSA-4x37-hw65-52w8
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-284: Improper Access Control
Affected Product Keycloak
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:L/UI:N/S:U/C:H/I:N/A:N).

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 None (I:N)
Availability None (A:N)

How to Fix CVE-2026-37979

To remediate this vulnerability, upgrade all affected Keycloak 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: 26.6.2 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-services</artifactId>
    <version>26.6.2</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-2026-37979, 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 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 26.6.2), 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-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In Keycloak, 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. This access control vulnerability in Keycloak's OpenID Connect (OIDC) token introspection endpoint allows a confidential client to bypass audience restrictions. An attacker-controlled client with valid credentials can retrieve sensitive token claims intended for other resource servers, compromising the confidentiality of lightweight access tokens. This issue can be exploited remotely by any confidential client in the realm with valid credentials.

CVE-2026-37979 Affected Keycloak Versions

1 component(s)
Fixed Versions:
26.6.2
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-services
maven/org.keycloak/keycloak-services
Maven
< 26.6.2
26.6.2

References

NVD — CVE-2026-37979 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-37979
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak/issues/49113
access.redhat.com/errata/rhsa-2026:19... WEB
https://access.redhat.com/errata/RHSA-2026:19596
access.redhat.com/errata/rhsa-2026:19... WEB
https://access.redhat.com/errata/RHSA-2026:19597
Keycloak Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-37979
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2455328
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak
Keycloak Release RELEASE
https://github.com/keycloak/keycloak/releases/tag/26.6.2

Frequently Asked Questions

What is CVE-2026-37979?
CVE-2026-37979 is a security vulnerability in Keycloak involving Information disclosure via OIDC token introspection endpoint audience bypass under CWE-284: Improper Access Control.
Which Keycloak versions are affected?
Affected versions include releases prior to 26.6.2 across affected packages: org.keycloak:keycloak-services.
What version fixes CVE-2026-37979?
Upgrading to 26.6.2 (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 26.6.2. Upgrade your dependency to 26.6.2 or later.
What is the CVSS score of CVE-2026-37979?
CVE-2026-37979 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-37979?
CVE-2026-37979 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check Maven dependencies for CVE-2026-37979?
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-4x37-hw65-52w8",
  "modified" : "2026-06-04T15:30:04Z",
  "published" : "2026-05-19T12:31:39Z",
  "aliases" : [ "CVE-2026-37979" ],
  "summary" : "Keycloak: Information disclosure via OIDC token introspection endpoint audience bypass",
  "details" : "A flaw was found in Keycloak. This access control vulnerability in Keycloak's OpenID Connect (OIDC) token introspection endpoint allows a confidential client to bypass audience restrictions. An attacker-controlled client with valid credentials can retrieve sensitive token claims intended for other resource servers, compromising the confidentiality of lightweight access tokens. This issue can be exploited remotely by any confidential client in the realm with valid credentials.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-services"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.6.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-37979"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/issues/49113"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:19596"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:19597"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-37979"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2455328"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/releases/tag/26.6.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-04T15:30:04Z",
    "nvd_published_at" : "2026-05-19T12:16:18Z"
  }
}