Excessive Platform Resource Consumption within a Loop in Keycloak - CVE-2026-4634
Published: September 10, 2026
Vulnerability identifier: #VU148936
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-4634
CWE-ID: CWE-1050
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to excessive platform resource consumption within a loop in the OpenID Connect token endpoint when processing a specially crafted POST request with an excessively long scope parameter. A remote attacker can send a specially crafted POST request with an excessively long scope parameter to cause a denial of service.
Affected software
Keycloak
Red Hat build of Keycloak
Red Hat build of Keycloak
How to mitigate CVE-2026-4634
Install security update from vendor's website.
Keycloak - update to 26.5.7
Red Hat build of Keycloak - addressed in versions 26.2.15, 26.4.11
Red Hat build of Keycloak - addressed in versions 26.2.15, 26.4.11