Keycloak HOTP Race Condition Enables OTP Replay
CVE-2026-118030 Published on October 29, 2026
Keycloak-services: keycloak-services: hotp race condition allows single otp code reuse across concurrent logins
A flaw was found in the HOTP authentication mechanism of the keycloak-services component, which provides identity and access management services. The issue occurs because the system validates a one-time password and updates its internal counter in two separate steps without proper locking. An attacker with a users password could exploit this timing gap to use a single one-time code to log in multiple times simultaneously.
Vulnerability Analysis
CVE-2026-118030 is exploitable with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality and integrity, and no impact on availability.
Timeline
Reported to Red Hat.
Made public.
Weakness Type
What is a Race Condition Vulnerability?
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.
CVE-2026-118030 has been classified to as a Race Condition vulnerability or weakness.
Products Associated with CVE-2026-118030
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