The Active Template Library (ATL) in Microsoft Windows 2000 SP4, XP SP2 and SP3, Server 2003 SP2, Vista Gold, SP1, and SP2, and Server 2008 Gold and SP2 allows remote attackers to execute arbitrary code via vectors related to erroneous free operations after reading a variant from a stream and deleting this variant, aka "ATL Object Type Mismatch Vulnerability."