The Key Distribution Center (KDC) in Kerberos in Microsoft Windows 2000 SP4, Server 2003 SP2, and Server 2008 Gold and SP2, when a trust relationship with a non-Windows Kerberos realm exists, allows remote authenticated users to cause a denial of service (NULL pointer dereference and domain controller outage) via a crafted Ticket Granting Ticket (TGT) renewal request, aka "Kerberos Null Pointer Dereference Vulnerability."