Software Engineering Institute

Microsoft Office Web Components are ActiveX controls that provide Microsoft Office functionality, such as spreadsheets, tables, and charts. These ActiveX controls are provided by the file MSOWC.DLL. Several of the ActiveX controls provided by MSOWC.DLL are marked Safe for Scripting and Safe for Initialization, which means that they can be controlled by a web page in Internet Explorer. Microsoft Office Web Components are provided by multiple products including

• Microsoft Office 2000
• Microsoft Office XP
• Visual Studio .NET 2002
• Visual Studio .NET 2003
• Microsoft BizTalk Server 2000
• Microsoft BizTalk Server 2002
• Microsoft Commerce Server 2000
• Internet Security and Acceleration Server 2000

By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), an attacker may be able to execute arbitrary code with the privileges of the user.

Apply an update
This issue is addressed in Microsoft Security Bulletin MS08-017. This update provides a newer version of MSOWC.DLL, sets the kill bit for the vulnerable versions of the Microsoft Office Spreadsheet control, and sets the phoenix bit to retain compatibility with web pages that refer to the old CLSID for the Spreadsheet control.

Disable the Microsoft Office Spreadsheet ActiveX control in Internet Explorer

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

{0002E510-0000-0000-C000-000000000046}
{0002E511-0000-0000-C000-000000000046}
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 this control:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E510-0000-0000-C000-000000000046}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{0002E511-0000-0000-C000-000000000046}]
"Compatibility Flags"=dword:00000400
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.