Microsoft DirectX Vulnerability Under Attack

Microsoft is investigating reports of a vulnerability in Microsoft DirectX that is under attack by hackers using malicious QuickTime videos.

According to a Microsoft advisory, the vulnerability can be exploited by hackers to remotely execute code with the rights of the logged-on user. Specifically, the vulnerability is in the QuickTime parser in Microsoft DirectShow, and is due to the way DirectShow handles supported QuickTime format files.

A feature of the Windows operating system, DirectX is used for streaming media to enable graphics and sound when playing games or watching video. Within DirectX, the DirectShow technology performs client-side audio and video sourcing, manipulation and rendering, while the QuickTime Movie Parser filter splits Apple QuickTime data into audio and video streams.

Although this isn't a browser vulnerability, Microsoft officials warned that because the vulnerability is in DirectShow, any browser using media plug-ins that use DirectShow is subject to attack. In addition, it is possible to direct calls to DirectShow specifically, even if Apple's QuickTime (which is not vulnerable) is installed. 

"While our investigation is ongoing, our investigation so far has shown that Windows 2000 Service Pack 4, Windows XP and Windows Server 2003 are vulnerable; all versions of Windows Vista and Windows Server 2008 are not vulnerable," the company said in the advisory. "Microsoft has activated its Software Security Incident Response Process (SSIRP) and is continuing to investigate this issue." 

There are a few workarounds available to help users deal with the threat. Administrators can disable QuickTime parsing in Quartz.dll by deleting the following registry key: 

HKEY_CLASSES_ROOT\CLSID\{D51BD5A0-7548-11CF-A520-0080C77EF58A} 

Users can also modify the ACL (access control list) on quartz.dll. Instructions for these and other workarounds are contained in the DirectShow security advisory.