Medium [CVE-2026-16103 +1] Incomplete fix for CIBA brute-force lockout bypass at token redemption
This medium-severity Red Hat Linux advisory covers CVE-2026-16103 and CVE-2026-9798 affecting Red Hat Build of Keycloak.
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Summary
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.
The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that successful exploitation allows an attacker to obtain a valid user session for an account that should be temporarily disabled by brute-force protection.
Successful exploitation requires a CIBA request to be in flight prior to the account lockout and necessitates user interaction for approval. The vulnerability's root cause is the omission of brute-force protector checks in the CIBA grant redemption code path.
Affected Red Hat products: Red Hat Build of Keycloak. Red Hat lists Red Hat Data Grid 8; Red Hat JBoss Enterprise Application Platform Expansion Pack; Red Hat Single Sign-On 7 as not affected.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
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