Vulnerability Note VU#210257

British Telecommunications Business Connect webhelper ActiveX control buffer overflows

Overview

The British Telecommunications Business Connect webhelper ActiveX control contains multiple buffer overflows, which can allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

I. Description

The registration process for British Telecommunications (BT) internet services uses an ActiveX control called webhelper. This ActiveX control is provided by the file btbconnectwebcontrol.dll. The BT Business Connect webhelper ActiveX control contains multiple buffer overflow vulnerabilities.

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. The attacker could also cause Internet Explorer (or the program using the WebBrowser control) to crash.

III. Solution

This issue is addressed in version 1.0.0.7 of the Business Connect webhelper ActiveX control. However, customers who have already gone through the registration process will not likely get the updated control. Therefore, please consider the following workarounds

Disable the BT Business Connect webhelper ActiveX control in Internet Explorer

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

{E82ED244-76EF-4D34-BDB3-AB21A522F38E}

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\{E82ED244-76EF-4D34-BDB3-AB21A522F38E}]

"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 Notified	Date Updated
BT	Vulnerable	18-May-2007

References

http://www.cert.org/tech_tips/securing_browser/#Internet_Explorer
http://support.microsoft.com/kb/240797
http://secunia.com/advisories/25472/

Credit

This vulnerability was reported by Will Dormann of CERT/CC.

This document was written by Will Dormann.

Other Information

Date Public:	2007-05-29
Date First Published:	2007-05-29
Date Last Updated:	2007-05-30
CERT Advisory:
CVE-ID(s):
NVD-ID(s):
US-CERT Technical Alerts:
Metric:	0.92
Document Revision:	8

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Produced 2007 by US-CERT, a government organization
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