Microsoft has released a security advisory on a vulnerability in the Microsoft Jet Database Engine that can be exploited through Microsoft Word.

Extracted from the advisory:
This is a code execution vulnerability caused by a buffer overrun in msjet40.dll, the Microsoft Jet Database Engine. An attacker can exploit this vulnerability by convincing a user to open a Word file that is constructed to load the specially crafted database file using msjet40.dll.

If the version of Msjet40.dll is lower than 4.0.9505.0, you have a vulnerable version of the Microsoft Jet Database Engine.

Customers using Microsoft Word 2000 Service Pack 3, Microsoft Word 2002 Service Pack 3, Microsoft Word 2003 Service Pack 2, Microsoft Word 2003 Service Pack 3, Microsoft Word 2007, and Microsoft Word 2007 Service Pack 1 on Microsoft Windows 2000, Windows XP, or Windows Server 2003 Service Pack 1 are vulnerable to these attacks.
 
However, Windows Server 2003 Service Pack 2, Windows Vista, and Windows Vista Service Pack 1 are not vulnerable to the buffer overrun being attacked, as they include a version of the Microsoft Jet Database Engine that is not vulnerable to this issue.

Recommendation: Do not open or save Word files that you receive from untrusted sources or that you receive unexpectedly from trusted sources. This vulnerability could be exploited when a user opens a specially crafted Word file.

http://www.microsoft.com/technet/security/advisory/950627.mspx