# Duplicate Advisory: Authentication bypass via jwt algorithm confusion

Source: https://junglewise.ai/threats/duplicate-advisory-authentication-bypass-via-jwt-algorithm-confusion-40489dee  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-26  
License: CC BY 4.0 with a link back

Severity: high · CVSS 8.1 · Published 2026-06-26

### 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This advisory has been withdrawn because it is a duplicate of GHSA-j97h-3f8r-mrjr.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.

Technologies: [org.keycloak:keycloak-services (Maven)](https://junglewise.ai/threats/technologies/org-keycloak-keycloak-services). Vendors: [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 8.1, published 26 June 2026.

**Which products and versions are affected?** org.keycloak:keycloak-services (Maven) < 26.6.4, ECOSYSTEM:introduced=0,fixed=26.6.4.

**Is there a fix for This vulnerability?** Yes. org.keycloak:keycloak-services (Maven): upgrade to 26.6.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected?** Check whether you run org.keycloak:keycloak-services (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.keycloak:keycloak-services (Maven): upgrade to 26.6.4 or later

  ```sh
  # set org.keycloak:keycloak-services to 26.6.4 in your pom.xml or build.gradle
  ```


## Affected products

- org.keycloak:keycloak-services (Maven) < 26.6.4, ECOSYSTEM:introduced=0,fixed=26.6.4

## Related threats

- [Keycloak unauthenticated account takeover via reset-credentials bypass](https://junglewise.ai/threats/cve-2026-18963-siemens-industrial-edge-management-authentication-bypass-in)
- [Keycloak JWT algorithm confusion in JWT Authorization Grant flow](https://junglewise.ai/threats/cve-2026-11800-keycloak-jwt-algorithm-confusion-in-jwt-authorization-grant-flow)
- [Duplicate Advisory: Keycloak vulnerable to authorization bypass via incorrect uri comparison](https://junglewise.ai/threats/duplicate-advisory-keycloak-vulnerable-to-authorization-bypass-via-009d6a49)
- [Duplicate Advisory: Keycloak vulnerable to cross-site scripting (xss) via case-insensitive uri validation bypass](https://junglewise.ai/threats/duplicate-advisory-keycloak-vulnerable-to-cross-site-scripting-xss-via-1687acae)
- [Duplicate Advisory: Keycloak allows unauthorized access to resources via uma permission ticket bypass](https://junglewise.ai/threats/duplicate-advisory-keycloak-allows-unauthorized-access-to-resources-via-1f5f5b83)