Vulnerability Note VU#654577

Microsoft Office Web Components Spreadsheet ActiveX control URL parsing stack buffer overflow

Overview

The Microsoft Office Web Components ActiveX controls contain a stack buffer overflow in the processing of URLs, which allows a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

I. Description

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

The Microsoft Office Spreadsheet control contains a stack buffer overflow in the handling of URLs.

II. Impact

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.

III. Solution

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_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX Compatibility{0002E510-0000-0000-C000-000000000046}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX 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.

Systems Affected

Vendor	Status	Date Updated
Microsoft Corporation	Vulnerable	12-Mar-2008

References

http://www.microsoft.com/technet/security/bulletin/ms08-017.mspx
http://blogs.technet.com/swi/archive/2008/02/06/The-Kill_2D00_Bit-FAQ_3A00_-Part-1-of-3.aspx
http://blogs.technet.com/swi/archive/2008/02/07/The-Kill_2D00_Bit-FAQ_3A00_-Post-2-of-3.aspx#PhoenixBit

Credit

This vulnerability was reported by Microsoft, who in turn credit Chris Ries of VigilantMinds and Xiao Hui of NCNIPC.

This document was written by Will Dormann.

Other Information

Date Public	03/11/2008
Date First Published	03/12/2008 02:54:15 PM
Date Last Updated	03/13/2008
CERT Advisory
CVE Name	CVE-2006-4695
US-CERT Technical Alerts
Metric	27.97
Document Revision	15