Review reviewHigh

CVE-2026-4634

Red Hat Red Hat build of Keycloak 26.2, Red Hat build of Keycloak 26.2.15, Red Hat build of Keycloak 26.4

A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.

CVSS: 7.5
EPSS: 0.52%
CISA KEV: Not listed
Published: 2026.04.02

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.52%

Technical severityCVSS 7.5

Vulnerability overview

Affected product and versions

Product: Red Hat Red Hat build of Keycloak 26.2, Red Hat build of Keycloak 26.2.15, Red Hat build of Keycloak 26.4
Affected versions: 26.2, 26.2.15, 26.4, 26.4.11
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that Red Hat Red Hat build of Keycloak 26.2, Red Hat build of Keycloak 26.2.15, Red Hat build of Keycloak 26.4 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-1050