---
id: CVE-2026-0976
title: A flaw was found in Keycloak
summary: >-
  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 re…
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-20
published: '2026-01-15'
updated: '2026-08-09'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-0976'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-0976'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2429869'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:2365'
    label: 'RHSA-2026:2365'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-0976'
  - url: 'https://github.com/advisories/GHSA-v897-pv23-r8cw'
tags:
  - nvd
  - cve.org
  - ghsa
  - maven
epss: 0.00489
epssPercentile: 0.41901
ingestedAt: '2026-08-09T19:34:40.616Z'
vendor: Red Hat
product: Red Hat build of Keycloak 26.4.9
affected:
  - build_of_keycloak_26.4.9
  - keycloak-quarkus-server (all versions)
  - keycloak-quarkus-server (all versions)
  - keycloak-quarkus-server-app (all versions)
  - keycloak-quarkus-server-deployment (all versions)
  - keycloak-quarkus-server (all versions)
  - keycloak-quarkus-server-app (all versions)
  - keycloak-quarkus-server-deployment (all versions)
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-01-15T14:44:09.361820Z'
aliases:
  - GHSA-v897-pv23-r8cw
ecosystem: maven
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-0976)

Affected packages:

- `org.keycloak:keycloak-quarkus-server <= 26.2.5`

Source: https://github.com/advisories/GHSA-v897-pv23-r8cw