Description
Keycloak provides a mechanism called Client Policies to enforce security requirements on clients, such as requiring them to use signed JWTs for authentication. A flaw was discovered where this enforcement can be bypassed. An attacker with valid client credentials can provide a fake, unsigned assertion header that tricks the system into thinking the policy requirements have been met. This allows the attacker to authenticate using simpler methods like a client secret even when the administrator has mandated more secure, signed assertions.
Affected products
redhat: build of keycloak; redhat: data grid; redhat: jboss enterprise application platform expansion pack; redhat: single sign-on
References4
- access.redhat.com/security/cve/CVE-2026-16093 Vendor Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2501729 Issue TrackingVendor Advisory
- access.redhat.com/errata/RHSA-2026:68277
- access.redhat.com/errata/RHSA-2026:68278
Metrics
- CVSS 3.1
-
5.4
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N - EPSS — exploit probability
- 0% percentile: 34 · as of 15 November 2026
- CWE
- CWE-807
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.