---
id: GHSA-gqj5-2xp5-3qmp
title: 'Duplicate Advisory: Authentication bypass via jwt algorithm confusion'
summary: 'Duplicate Advisory: 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: '2026-06-26'
updated: '2026-11-03'
sourceUpdated: '2026-11-03T17:24:15Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-gqj5-2xp5-3qmp'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11800'
  - 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://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-11800.json
  - url: 'https://github.com/advisories/GHSA-gqj5-2xp5-3qmp'
tags:
  - ghsa
  - maven
ingestedAt: '2026-11-03T17:50:48.253Z'
---

## Overview

### Duplicate Advisory
This advisory has been withdrawn because it is a duplicate of GHSA-j97h-3f8r-mrjr. This link is maintained to preserve external references.

### Original 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`