Brute-Force Token Redemption Loophole in Keycloak CIBA (keycloak-services)
CVE-2026-16103 Published on July 17, 2026
Keycloak-services: keycloak-services: incomplete fix for ciba brute-force lockout bypass at token redemption
A flaw was found in the keycloak-services component of Keycloak. This issue is an incomplete fix for CVE-2026-9798, where brute-force protection checks were added to the Client-Initiated Backchannel Authentication (CIBA) initiation handler but were omitted from the token redemption handler. This allows an attacker with valid client credentials to obtain access and refresh tokens for a user account that has been locked due to brute-force protection, provided the authentication request was started before the lockout occurred and was approved by the user.
Vulnerability Analysis
CVE-2026-16103 can be exploited with network access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity and availability.
Timeline
Reported to Red Hat.
Made public.
Weakness Type
Improper Enforcement of Behavioral Workflow
The software supports a session in which more than one behavior must be performed by an actor, but it does not properly ensure that the actor performs the behaviors in the required sequence.
Products Associated with CVE-2026-16103
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Affected Versions
Red Hat Build of Keycloak: Red Hat Build of Keycloak: Red Hat Build of Keycloak: Red Hat Data Grid 8: Red Hat JBoss Enterprise Application Platform Expansion Pack: Red Hat Single Sign-On 7:Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.