By taking advantage of flaws in Windows memory allocation functions, it is possible to knock over machines running Windows XP SP1 and Windows 2000 SP4 in certain configurations, it has been revealed. When a malformed request is made to the UPnP service in the data section of a call to the GetDeviceList function, this can be achieved. Proof-of-concept code has been developed by hackers that exploits this. Microsoft users running Windows XP Service Pack 2, Windows Server 2003 and Windows Server 2003 Service Pack 1 do not have to concern themselves with this issue, since these systems are not vulnerable in this way.
This vulnerability manifests itself when a malformed request is made to the UPnP service in the data section of a call to the GetDeviceList function. In handling this request, memory consumption on vulnerable Windows boxes increase to the point where the system becomes unresponsive. Repeated requests can therefore be used to mount denial of service attacks.
Winny Thomas of Nevis Labs in India, the security researcher who developed the proof-of-concept code, readily concedes the Windows RPC memory allocation remote denial of service exploit he highlights is only a moderate risk. Microsoft is yet to develop a security fix. It criticises Thomas of publicising details of the flaw through FrSIRT, a full disclosure web site, instead of submitting it to Microsoft directly first.