Affected versions of MISP use Redis to throttle repeated authentication-failure log entries. The intent is to avoid excessive duplicate logs while still recording failed authentication activity. However, User->setupRedis() returns false when Redis cannot be reached. The vulnerable _shouldLog() logic only returned true when a Redis instance existed and no throttle key was present. Therefore, when Redis was unavailable, the function did not allow the log write at all, effectively silencing authentication-failure logging for the duration of the outage. Version affected: ≤2.5.45