CVE-2026-9798
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.
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.
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | N/A | 4.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
Acknowledgements
Red Hat would like to thank Evan Hendra (Independent Security Researcher) for reporting this issue.
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