Heap-based buffer overflow in the WMCheckURLScheme function in WMVCORE.DLL in Microsoft Windows Media Player (WMP) 10.00.00.4036 on Windows XP SP2, Server 2003, and Server 2003 SP1 allows remote attackers to cause a denial of service (application crash) and execute arbitrary code via a long HREF attribute, using an unrecognized protocol, in a REF element in an ASX PlayList file.