An unpatched security flaw in Microsoft's Jet Database Engine is being used to launch targeted attacks against Windows users, according to an advisory from the software vendor.
The attacks, described by Microsoft as "very limited," are exploiting a buffer overrun vulnerability in the lightweight database that provides data access to applications such as Microsoft Access, Microsoft Visual Basic and third-party applications
Technical details on this zero-day vulnerability are not yet available but it is common knowledge that the Jet DB engine has suffered from major security issues over the last few years.
In fact, proof-of-concept exploit code targeting multiple Jet database engine flaws has been available on the Internet since April 2005. The public exploit code affects the same "msjet40.dll" component referenced in Microsoft's pre-patch advisory.
"If the version of Msjet40.dll is lower than 4.0.9505.0, you have a vulnerable version of the Microsoft Jet Database Engine," Microsoft warned.
Although publicly known Jet DB flaws have remained unpatched for years, Microsoft said customers running Windows Server 2003 Service Pack 2, Windows Vista, and Windows Vista Service Pack 1 are not vulnerable to this issue. This suggests the vulnerability was silently fixed-without public documentation-in recent service packs.
According to Microsoft's advisory, an attacker could host a Web site that contains a specially crafted Word document to trigger the vulnerability.
"In addition, compromised Web sites and Web sites that accept or host user-provided content could contain specially crafted content that could exploit this vulnerability," the company said, noting that an attacker would have no way to force users to visit these Web sites.
This suggests that social engineering lures are being used in the targeted attacks. These could include links spammed via e-mail, or sent via instant messenger chat sessions.
SOFTWARE AFFECTED BY THIS ISSUE:
- 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
- Microsoft Word 2007 Service Pack 1 on Microsoft Windows 2000
- Windows XP
- Windows Server 2003 Service Pack 1
NOT AFFECTED BY THIS ISSUE:
- Windows Server 2003 Service Pack 2
- Windows Vista
- Windows Vista Service Pack 1
In the absence of a patch, Microsoft recommends:
- Restricting the Microsoft Jet Database Engine from running
- Blocking MDB files from being processed through your mail infrastructure.