---
id: CVE-2026-11800
aliases:
  - GHSA-j97h-3f8r-mrjr
title: Keycloak has authentication bypass via jwt algorithm confusion
summary: Keycloak has authentication bypass via jwt algorithm confusion
severity: high
cvss: 8.1
cwe:
  - CWE-347
vendor: keycloak
product: 'org.keycloak:keycloak-services'
ecosystem: maven
affected:
  - 'org.keycloak:keycloak-services < 26.6.4'
patched:
  - 'org.keycloak:keycloak-services 26.6.4'
published: '2026-11-03'
updated: '2026-11-03'
sourceUpdated: '2026-11-03T17:24:30Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-j97h-3f8r-mrjr'
references:
  - url: >-
      https://github.com/keycloak/keycloak/security/advisories/GHSA-j97h-3f8r-mrjr
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11800'
  - url: 'https://github.com/keycloak/keycloak/issues/50357'
  - url: 'https://github.com/keycloak/keycloak/pull/50374'
  - url: >-
      https://github.com/keycloak/keycloak/commit/6d61885f20ac59a2ff8b823fc9ed1f1ef1019951
  - url: >-
      https://github.com/keycloak/keycloak/commit/d343c7373dcc7bfeb9dc14de2309836299c81837
  - url: 'https://access.redhat.com/errata/RHSA-2026:30083'
  - url: 'https://access.redhat.com/errata/RHSA-2026:30084'
  - url: 'https://access.redhat.com/security/cve/CVE-2026-11800'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2487006'
  - url: 'https://github.com/keycloak/keycloak/releases/tag/26.6.4'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-11800.json
  - url: 'https://github.com/advisories/GHSA-j97h-3f8r-mrjr'
tags:
  - ghsa
  - maven
epss: 0.003
epssPercentile: 0.22775
ingestedAt: '2026-11-03T17:50:48.252Z'
---

## Overview

### Description
A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.

## Affected packages

- `org.keycloak:keycloak-services < 26.6.4`

## Remediation

Upgrade to a patched release:

- `org.keycloak:keycloak-services 26.6.4`