Software Engineering Institute

Microsoft Snapshot Viewer is a viewer for snapshots created with Microsoft Access. Snapshot Viewer is available as an ActiveX control, which is provided by snapview.ocx, or as a stand-alone application. Snapshot Viewer is provided with Office 2000, Office XP, and Office 2003, and it may also be installed on a system that does not have Microsoft Office. By design, the Snapshot Viewer ActiveX control can download a specified file to a temporary location, giving it a temporary name. However, a race condition in the control can allow an attacker to download files to arbitrary locations with arbitrary file names.

We have received reports of active exploitation of this vulnerability. Exploit code for this vulnerability is publicly available.

By convincing a victim to view an HTML document (web page, HTML email, or email attachment), an attacker could download arbitrary files to a vulnerable system within the security context of the user running IE. These files could contain code that could be executed through other means. The user may click the file inadvertently, or the file may be placed in a sensitive location, such as the Windows Startup folder where it will automatically execute the next time the user logs onto the system.

Apply an update
This issue is addressed in Microsoft Security Bulletin MS08-041.

Disable the Microsoft Snapshot Viewer ActiveX control in Internet Explorer

The vulnerable ActiveX control can be disabled in Internet Explorer by setting the kill bit for the following CLSIDs:

{F0E42D50-368C-11D0-AD81-00A0C90DC8D9}
{F0E42D60-368C-11D0-AD81-00A0C90DC8D9}
{F2175210-368C-11D0-AD81-00A0C90DC8D9}
More information about how to set the kill bit is available in Microsoft Support Document 240797. Alternatively, the following text can be saved as a .REG file and imported to set the kill bit for these controls:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{F0E42D50-368C-11D0-AD81-00A0C90DC8D9}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{F0E42D60-368C-11D0-AD81-00A0C90DC8D9}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{F2175210-368C-11D0-AD81-00A0C90DC8D9}]
"Compatibility Flags"=dword:00000400
Upgrade to Internet Explorer 7

Upgrading Internet Explorer to version 7 or later may help mitigate this vulnerability through its ActiveX opt-in feature. This feature is designed to prompt the user before using ActiveX controls that are already installed on the system.

Do not run Windows with administrator privileges

Running Windows using an unprivileged regular user account may mitigate the affects of this vulnerability. See the Microsoft Technet article Applying the Principle of Least Privilege to User Accounts on Windows XP for more information. This can prevent an attacker from being able to download files to the Startup folder for "All Users."

Disable ActiveX

Disabling ActiveX controls in the Internet Zone (or any zone used by an attacker) appears to prevent exploitation of this and other ActiveX vulnerabilities. Instructions for disabling ActiveX in the Internet Zone can be found in the "Securing Your Web Browser" document.