Vulnerability Note VU#184473

Microgaming Download Helper ActiveX control stack buffer overflow

Overview

The Microgaming Download Helper ActiveX control contains a stack buffer overflow, which can allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

I. Description

Microgaming provides software for online gaming, including online casinos. The Microgaming Download Helper ActiveX control, provided by dlhelper.dll, is vulnerable to stack buffer overflow. Older versions of the control are referred to as "WebHandler Class."

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 the web browser to crash.

III. Solution

Apply an update

This issue is addressed in version 7.2.0.19 of the Download Helper ActiveX control. Users of the Download Helper ActiveX control can perform the update by following these steps:

Go to %windir%\Downloaded Program Files\
Right-click on Download Helper Class
Click Update
Verify that the control is updated to version 7.2.0.19 or later

This ActiveX control has also been disabled in Internet Explorer with the update for Microsoft Security Advisory (956391).

If the above steps did not succeed, or if the system has the older "WebHandler Class" control, please use the following workarounds

Disable the Download Helper ActiveX control in Internet Explorer

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

{AED98630-0251-4E83-917D-43A23D66D507}

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\{AED98630-0251-4E83-917D-43A23D66D507}]

"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
Microgaming Software Systems Limited	Vulnerable	2006-09-29	2007-04-23

References

http://www.cert.org/tech_tips/securing_browser/#Internet_Explorer
http://www.microsoft.com/technet/security/advisory/956391.mspx
http://www.microgaming.com/
http://support.microsoft.com/kb/240797
http://secunia.com/advisories/25017/

Credit

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

This document was written by Will Dormann.

Other Information

Date Public:	2007-04-23
Date First Published:	2007-04-23
Date Last Updated:	2008-10-14
CERT Advisory:
CVE-ID(s):
NVD-ID(s):
US-CERT Technical Alerts:
Metric:	2.45
Document Revision:	10

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Produced 2007 by US-CERT, a government organization
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