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Review reviewHigh

CVE-2026-11800

Red Hat Red Hat build of Keycloak 26.6, Red Hat build of Keycloak 26.6.4, Red Hat Build of Keycloak

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.

CVSS
8.1
EPSS
0.18%
7.88% percentile
CISA KEV
Not listed
Published
2026.06.26
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.18%
Technical severityCVSS 8.1

Vulnerability overview

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 product and versions

Product
Red Hat Red Hat build of Keycloak 26.6, Red Hat build of Keycloak 26.6.4, Red Hat Build of Keycloak
Affected versions
>= 26.6 < 26.6.4
Fixed versions
26.6.4

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Red Hat Red Hat build of Keycloak 26.6, Red Hat build of Keycloak 26.6.4, Red Hat Build of Keycloak and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CWE
CWE-347