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MEDIUM

Keycloak: keycloak: brute-force protection bypass in ciba flow

Published May 28, 2026

Description

A flaw was found in Keycloak, an open-source identity and access management solution. When a user account is temporarily locked due to repeated failed login attempts, an attacker with valid client credentials can exploit the Client-Initiated Backchannel Authentication (CIBA) flow to bypass this brute-force protection. This allows continued authentication attempts and token issuance even when the account should be locked, potentially enabling further unauthorized access attempts.

Affected products

Remediation

Vendor solution

To mitigate this issue, ensure that Client-Initiated Backchannel Authentication (CIBA) is not enabled in Keycloak realms unless explicitly required. If CIBA is enabled, consider disabling it to prevent the bypass of brute-force protection mechanisms. Consult Keycloak documentation for instructions on managing CIBA configuration.

Red Hat statement

This flaw in Keycloak's Client-Initiated Backchannel Authentication (CIBA) flow is rated as Low impact. The vulnerability allows bypassing brute-force protection when a user account is locked, but only if CIBA is explicitly enabled and configured (non-default), and the user approves the authentication request on their device. This significantly limits the attack surface in typical Red Hat deployments where CIBA is not enabled by default.

Red Hat mitigation

To mitigate this issue, ensure that Client-Initiated Backchannel Authentication (CIBA) is not enabled in Keycloak realms unless explicitly required. If CIBA is enabled, consider disabling it to prevent the bypass of brute-force protection mechanisms. Consult Keycloak documentation for instructions on managing CIBA configuration.

Weaknesses (1)

References (16)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner redhat
Published May 28, 2026
Updated Aug 20, 2026
Reserved May 28, 2026
CISA Vulnrichment
Updated May 29, 2026
NVD
Status Modified
Modified Aug 20, 2026
Red Hat
Severity Moderate
Public date May 28, 2026
GHSA-Q6H7-XXP7-7429