EUVD-2026-45225Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
OAuth client credentials required (PR:L); specific race-condition timing between CIBA approval and account lockout raises complexity (AC:H); only token confidentiality disclosed (C:L).
Primary rating from Vendor (redhat).
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
Lifecycle Timeline
1DescriptionNVD
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.
AnalysisAI
Brute-force lockout bypass in Keycloak's Client-Initiated Backchannel Authentication (CIBA) flow allows an attacker holding valid OAuth client credentials to redeem previously approved authentication requests and obtain access and refresh tokens for a user account that has since been locked. This is an incomplete fix for CVE-2026-9798: the brute-force protection check was applied to the CIBA initiation handler but was never added to the token redemption handler, creating a gap that persists after the earlier patch. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three concurrent conditions: (1) the attacker must possess valid OAuth client credentials (client_id and client_secret) for a client registered in the target Keycloak realm - these are application-level secrets, not user passwords; (2) the target user account must have an active, user-approved CIBA authentication request that was initiated before the account became locked - this means the user must have actively approved the back-channel authentication prompt; and (3) the user account must subsequently enter a locked state due to brute-force protection before the attacker redeems the auth_req_id at the token endpoint. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The real-world risk is moderate and scenario-constrained. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who controls a registered OAuth client in the Keycloak realm initiates a CIBA authentication request for a targeted user account and waits for the user to approve the push notification or out-of-band prompt - which the user does, believing it to be a legitimate sign-in. If the target user's account is then locked by brute-force protection (whether triggered by the attacker on a separate channel or by prior failed attempts), the attacker can still call the CIBA token redemption endpoint with the approved auth_req_id and receive valid access and refresh tokens, effectively bypassing the lockout mechanism. … |
| Remediation | Patch availability has not been confirmed with an exact fix version from the available references; a Red Hat vendor advisory exists at https://access.redhat.com/security/cve/CVE-2026-16103 and should be checked for updated package versions. … Detailed patch versions, workarounds, and compensating controls in full report. |
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