Kerberos in Microsoft Windows Vista SP2, Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, and Windows 10 Gold and 1511 does not properly validate password changes, which allows remote attackers to bypass authentication by deploying a crafted Key Distribution Center (KDC) and then performing a sign-in action, aka "Windows Kerberos Security Feature Bypass."