A concurrency flaw in Keycloak's login-failure storage component affects deployments using MySQL or MariaDB in multi-node configurations. Simultaneous failed login attempts for the same account can cause a synchronization error that locks the user's database record, blocking legitimate login attempts. Additionally, some failed attempts may not be recorded properly, potentially bypassing brute-force protection. The issue is rated medium severity with a CVSS score of 4.8. No effective mitigation or patch is currently available according to the vendor advisory.