CVE-2026-2603: Keycloak Unauthorized Authentication Vulnerability

HIGH
Advisory Identifier: GHSA-x4p7-7chp-64hq
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CVSS 8.1
CWE-306
Published
Advisory Summary

CVE-2026-2603 is a HIGH (CVSS 8.1) unauthorized authentication vulnerability (CWE-306: Missing Authentication for Critical Function) affecting Keycloak libraries in the Maven ecosystem. The issue involves unauthorized authentication via disabled saml identity provider. Remediation is available by upgrading affected packages to version 26.5.5.

CVE-2026-2603 at a Glance

CVE Identifier CVE-2026-2603
GHSA Identifier GHSA-x4p7-7chp-64hq
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-306: Missing Authentication for Critical Function
Affected Product Keycloak
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.1

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

How to Fix CVE-2026-2603

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: 26.5.5 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-services</artifactId>
    <version>26.5.5</version>
</dependency>
org.keycloak:keycloak-server-spi-private fixed: 26.5.5 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-server-spi-private</artifactId>
    <version>26.5.5</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-2026-2603, 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 26.5.5), 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-306: Missing Authentication for Critical Function, where the product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. 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. A remote attacker could bypass security controls by sending a valid SAML response from an external Identity Provider (IdP) to the Keycloak SAML endpoint for IdP-initiated broker logins. This allows the attacker to complete broker logins even when the SAML Identity Provider is disabled, leading to unauthorized authentication.

CVE-2026-2603 Affected Keycloak Versions

2 component(s)
Fixed Versions:
26.5.5
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-services
maven/org.keycloak/keycloak-services
Maven
< 26.5.5
26.5.5
org.keycloak:keycloak-server-spi-private
maven/org.keycloak/keycloak-server-spi-private
Maven
< 26.5.5
26.5.5

References

NVD — CVE-2026-2603 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2603
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak/issues/46911
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak/pull/46932
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/4fd5367e6cc28cfa68fb2240fc459c12b1fdbf2a
Security Fix Commit FIX COMMIT
https://github.com/keycloak/keycloak/commit/8ed7e59dc08d79751a27c23aadb590f06b43f132
access.redhat.com/errata/rhsa-2026:39... WEB
https://access.redhat.com/errata/RHSA-2026:3925
access.redhat.com/errata/rhsa-2026:39... WEB
https://access.redhat.com/errata/RHSA-2026:3926
access.redhat.com/errata/rhsa-2026:39... WEB
https://access.redhat.com/errata/RHSA-2026:3947
access.redhat.com/errata/rhsa-2026:39... WEB
https://access.redhat.com/errata/RHSA-2026:3948
Keycloak Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-2603
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2440300
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak
Keycloak Source Repository REPOSITORY
https://github.com/keycloak/keycloak/commits/26.5.5

Frequently Asked Questions

What is CVE-2026-2603?
CVE-2026-2603 is a security vulnerability in Keycloak involving Unauthorized authentication via disabled SAML Identity Provider under CWE-306: Missing Authentication for Critical Function.
Which Keycloak versions are affected?
Affected versions include releases prior to 26.5.5 across affected packages: org.keycloak:keycloak-services, org.keycloak:keycloak-server-spi-private.
What version fixes CVE-2026-2603?
Upgrading to 26.5.5 (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 26.5.5. Upgrade your dependency to 26.5.5 or later.
Is keycloak-server-spi-private affected?
Yes, org.keycloak:keycloak-server-spi-private is affected in releases prior to 26.5.5. Upgrade your dependency to 26.5.5 or later.
What is the CVSS score of CVE-2026-2603?
CVE-2026-2603 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-2603?
CVE-2026-2603 is classified under CWE-306: Missing Authentication for Critical Function (The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.).
How can I check Maven dependencies for CVE-2026-2603?
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-x4p7-7chp-64hq",
  "modified" : "2026-05-20T01:09:01Z",
  "published" : "2026-03-18T03:32:09Z",
  "aliases" : [ "CVE-2026-2603" ],
  "summary" : "Keycloak: Unauthorized authentication via disabled SAML Identity Provider",
  "details" : "A flaw was found in Keycloak. A remote attacker could bypass security controls by sending a valid SAML response from an external Identity Provider (IdP) to the Keycloak SAML endpoint for IdP-initiated broker logins. This allows the attacker to complete broker logins even when the SAML Identity Provider is disabled, leading to unauthorized authentication.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-services"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.5"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-server-spi-private"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-2603"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/issues/46911"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/pull/46932"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/4fd5367e6cc28cfa68fb2240fc459c12b1fdbf2a"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commit/8ed7e59dc08d79751a27c23aadb590f06b43f132"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3925"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3926"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3947"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2026:3948"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-2603"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2440300"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/keycloak/keycloak/commits/26.5.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-306" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-18T20:17:33Z",
    "nvd_published_at" : "2026-03-18T02:16:24Z"
  }
}