Improper access control in Keycloak - CVE-2021-4133
Published: December 22, 2021 / Updated: June 29, 2026
Vulnerability identifier: #VU59083
CSH Severity: Low
CVSS v4: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-4133
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to gain unauthorized access to otherwise restricted functionality.
The vulnerability exists due to improper access restrictions within the administrative REST API. A remote user can bypass implemented security restrictions and create new default user accounts, even when new user registration is disabled.
Affected software
Keycloak
Red Hat Single Sign-On
Rational Test Automation Server
rh-sso7-keycloak (Red Hat package)
Red Hat Single Sign-On
Rational Test Automation Server
rh-sso7-keycloak (Red Hat package)
How to mitigate CVE-2021-4133
Install updates from vendor's website.
Keycloak - update to 15.1.1
Red Hat Single Sign-On - addressed in versions 7.5.0, 7.5.1
Rational Test Automation Server - update to 10.5
rh-sso7-keycloak (Red Hat package) - update to 15.0.2-3.redhat_00002.1.el7sso
Red Hat Single Sign-On - addressed in versions 7.5.0, 7.5.1
Rational Test Automation Server - update to 10.5
rh-sso7-keycloak (Red Hat package) - update to 15.0.2-3.redhat_00002.1.el7sso