CVE-2026-9798

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

Published May 28, 2026 CVSS 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Workaround

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.

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-q6h7-xxp7-7429 Keycloak has an Authentication Bypass by Primary Weakness
History
Type Values Removed Values Added
CPEs cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:-:*:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Redhat build Of Keycloak
Vendors & Products Redhat build Of Keycloak
Type Values Removed Values Added
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.
Title Keycloak: keycloak: brute-force protection bypass in ciba flow
First Time appeared Redhat
Redhat build Keycloak
Weaknesses CWE-305
CPEs cpe:/a:redhat:build_keycloak:
Vendors & Products Redhat
Redhat build Keycloak
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Aug 20, 2026, 12:54 AM
Reserved
May 28, 2026, 3:51 AM
Status
Modified
Published
May 28, 2026, 6:16 AM
Modified
Oct 26, 2026, 12:10 PM
Severity
Moderate
Public date
May 28, 2026, 3:53 AM