CVE-2026-0976: Keycloak quarkus server Keycloak Has An Improper Input Vulnerability

LOW
Advisory Identifier: GHSA-v897-pv23-r8cw
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CVSS 3.7
CWE-20
Published
Advisory Summary

CVE-2026-0976 is a LOW (CVSS 3.7) keycloak has an improper input vulnerability (CWE-20: Improper Input Validation) affecting Keycloak quarkus server libraries in the Maven ecosystem. The issue involves keycloak has an improper input validation vulnerability. Remediation is available in the latest vendor maintenance releases.

CVE-2026-0976 at a Glance

CVE Identifier CVE-2026-0976
GHSA Identifier GHSA-v897-pv23-r8cw
Severity LOW
CVSS v3.1 Base Score 3.7
CWE Classification CWE-20: Improper Input Validation
Affected Product Keycloak quarkus server
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:L/I:N/A:N).

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 Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-0976

To remediate this vulnerability, upgrade all affected Keycloak quarkus server 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-quarkus-server fixed: Latest secure release 
<dependency>
    <groupId>org.keycloak</groupId>
    <artifactId>keycloak-quarkus-server</artifactId>
    <version>Latest secure release</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-2026-0976, 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 quarkus server in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), 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-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Keycloak quarkus server, 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 improper input validation vulnerability occurs because Keycloak accepts RFC-compliant matrix parameters in URL path segments, while common reverse proxy configurations may ignore or mishandle them. A remote attacker can craft requests to mask path segments, potentially bypassing proxy-level path filtering. This could expose administrative or sensitive endpoints that operators believe are not externally reachable.

CVE-2026-0976 Affected Keycloak quarkus server Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
org.keycloak:keycloak-quarkus-server
maven/org.keycloak/keycloak-quarkus-server
Maven
≤ 26.2.5

References

NVD — CVE-2026-0976 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-0976
Keycloak quarkus server Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-0976
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2429869
Keycloak quarkus server Source Repository REPOSITORY
https://github.com/keycloak/keycloak

Frequently Asked Questions

What is CVE-2026-0976?
CVE-2026-0976 is a security vulnerability in Keycloak quarkus server involving Keycloak has an improper input validation vulnerability under CWE-20: Improper Input Validation.
Which Keycloak quarkus server versions are affected?
Affected versions include releases prior to current release patches across affected packages: org.keycloak:keycloak-quarkus-server.
What version fixes CVE-2026-0976?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is keycloak-quarkus-server affected?
Yes, org.keycloak:keycloak-quarkus-server is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-0976?
CVE-2026-0976 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:L/I:N/A:N.
What CWE is associated with CVE-2026-0976?
CVE-2026-0976 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check Maven dependencies for CVE-2026-0976?
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-v897-pv23-r8cw",
  "modified" : "2026-01-15T23:10:39Z",
  "published" : "2026-01-15T15:31:17Z",
  "aliases" : [ "CVE-2026-0976" ],
  "summary" : "Keycloak has an improper input validation vulnerability",
  "details" : "A flaw was found in Keycloak. This improper input validation vulnerability occurs because Keycloak accepts RFC-compliant matrix parameters in URL path segments, while common reverse proxy configurations may ignore or mishandle them. A remote attacker can craft requests to mask path segments, potentially bypassing proxy-level path filtering. This could expose administrative or sensitive endpoints that operators believe are not externally reachable.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.keycloak:keycloak-quarkus-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "26.2.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-0976"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-0976"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2429869"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/keycloak/keycloak"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-01-15T23:10:39Z",
    "nvd_published_at" : "2026-01-15T13:16:04Z"
  }
}