The Windows Metafile vulnerability is a vulnerability in Microsoft Windows which was first disclosed on Bugtraq on 27 December 2005, and subsequently used in a variety of exploits. The vulnerability, located in gdi32.dll, arises from the way in which Windows operating systems handle Windows Metafile (WMF) vector images, and permits arbitrary code to be executed on affected computers without the permission of their users. Windows versions from Windows 98 to Windows Server 2003 R2 are known to be vulnerable to the exploit, while versions as old as Windows 3.0 are probably also vulnerable. Exploits of this vulnerability are thus among the very few examples of genuine drive-by download.
Computers that are not running the Windows operating system are not affected. However, operating systems that have third-party programs or libraries that allow the execution of WMF files on non-Windows systems, are potentially vulnerable.
for more info, pls refer to
wiki