Keycloak JWT Algorithm Confusion Bypass Via Authorization Grant
CVE-2026-11800 Published on June 25, 2026

Org.keycloak:keycloak-services: keycloak: authentication bypass via jwt algorithm confusion
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.

Vendor Advisory Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-11800 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
NONE

Timeline

Reported to Red Hat.

Made public.

Weakness Type

Improper Verification of Cryptographic Signature

The software does not verify, or incorrectly verifies, the cryptographic signature for data.


Products Associated with CVE-2026-11800

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Red Hat Build Keycloak
 
Red Hat Jboss Data Grid
 
Red Hat Jbosseapxp
 
Red Hat Single Sign On
 

Affected Versions

Red Hat build of Keycloak 26.6: Red Hat build of Keycloak 26.6: Red Hat build of Keycloak 26.6: Red Hat build of Keycloak 26.6.4: Red Hat Build of Keycloak: Red Hat Build of Keycloak: Red Hat Data Grid 8: Red Hat JBoss Enterprise Application Platform Expansion Pack: Red Hat Single Sign-On 7: