CVE-2026-11800
Received Received - Intake
JWT Algorithm Confusion in Keycloak

Publication date: 2026-06-25

Last updated on: 2026-06-25

Assigner: Red Hat, Inc.

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.
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Meta Information
Published
2026-06-25
Last Modified
2026-06-25
Generated
2026-06-26
AI Q&A
2026-06-26
EPSS Evaluated
N/A
NVD
CVE-2026-11800
EUVD
EUVD-2026-39567
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
redhat keycloak *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-347 The product does not verify, or incorrectly verifies, the cryptographic signature for data.
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Executive Summary

This vulnerability is a JWT algorithm confusion flaw found in Keycloak's JWT Authorization Grant flow. It allows an attacker who already has valid client credentials to bypass the signature verification process by forging an assertion. As a result, the attacker can create unauthorized access tokens.

This enables the attacker to impersonate any federated user linked to the affected Identity Provider.

Impact Analysis

The vulnerability can lead to unauthorized access and potential privilege escalation. An attacker exploiting this flaw can impersonate any federated user, gaining access to resources and data they should not be able to access.

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