We’ve just released Microsoft Security Advisory 971778 today. This discusses a new vulnerability in Microsoft DirectShow affecting Windows 2000, Windows XP and Windows Server 2003 that is under limited attack. The advisory outlines information about the vulnerability and steps customers can take to protect themselves while we’re working on a security update to address the issue.
Our investigation has shown that the vulnerable code was removed as part of our work building Windows Vista. This means that Windows Vista and versions of Windows since Windows Vista (Windows Server 2008, Windows 7) are not vulnerable.
The vulnerability is in the QuickTime parser in Microsoft DirectShow. An attacker would try and exploit the vulnerability by crafting a specially formed video file and then posting it on a website or sending it as an attachment in e-mail. While this isn’t a browser vulnerability, because the vulnerability is in DirectShow, a browser-based vector is potentially accessible through any browser using media plug-ins that use DirectShow. Also, we’ve verified that it is possible to direct calls to DirectShow specifically, even if Apple’s QuickTime (which is not vulnerable) is installed.
Our investigation has found three workarounds that you can implement to protect yourself and we’ve documented these in the security advisory. In addition, we’ve got more technical details on the workarounds and the issue over at the Security Research and Defense (SRD) blog.
Most importantly, we have found one workaround in particular that is simple and effective and protects against the vulnerability with limited impact. In fact, this particular workaround is simple enough that we’ve been able to give you a way to automatically implement the workaround with the click of a button. Our Customer Service and Support (CSS) group has a new capability called “Fix it” that can automatically apply simple solutions to your system. We’ve gone ahead and built a “Fix it” that implements the “Disable the parsing of QuickTime content in quartz.dll” registry change workaround. We have also built a “Fix it” that will undo the workaround automatically.
To automatically implement the workaround, go to the KB article for the advisory. In the KB article, there’s a section titled “Fix it for me”. Click on the “Fix this problem” button under “Enable Workaround” in that section. You will then be offered an installer package from the Microsoft website. After you’ve confirmed that you trust the source of this package, run it on your system. The package will automatically set the appropriate registry keys on your system to implement the workaround. When you want to undo the workaround, click on the “Fix this problem” button under “Disable Workaround” in the same section.
We’re also sharing information about this vulnerability and the limited attacks that we’ve seen with partners in our Microsoft Active Protections Program (MAPP) and our Microsoft Security Response Alliance (MSRA) program to provide information that they can use to provide broader protections to customers.
As always, we’ll continue monitoring the situation and providing more information through the security advisory and the MSRC weblog.
*This posting is provided “AS IS” with no warranties, and confers no rights*