The Security Account Manager Remote (SAMR) protocol implementation in Microsoft Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, and Windows Server 2012 Gold and R2 does not properly determine the user-lockout state, which makes it easier for remote attackers to bypass the account lockout policy and obtain access via a brute-force attack, aka "SAMR Security Feature Bypass Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2014/ms14-016