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

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Summary

CVECVE-2026-9798
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-28 06:16:29 UTC
Updated2026-06-03 19:38:30 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 4.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

EPSS: 0.000530000 probability, percentile 0.169790000 (date 2026-06-01)

Problem Types: CWE-305 | CWE-305 Authentication Bypass by Primary Weakness

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
3.1CNACVSS4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Redhat Build Of Keycloak - All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat Build Of Keycloak Not specified Not specified

References

ReferenceSourceLinkTags
access.redhat.com/security/cve/CVE-2026-9798 [email protected] access.redhat.com Mitigation, Vendor Advisory
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com Issue Tracking, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Red Hat would like to thank Evan Hendra (Independent Security Researcher) for reporting this issue. (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-05-28T03:49:51.972ZReported to Red Hat.
CNA2026-05-28T03:53:01.734ZMade public.

Workarounds

CNA: 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.

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