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Microsoft HTML Help ActiveX control fails to properly validate input

Vulnerability Note VU#563756

Original Release Date: 2007-02-13 | Last Revised: 2007-02-23


The Microsoft HTML Help ActiveX control fails to properly validate input, which could allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.


The HTML Help Control (HHCtrl Object) is a Windows ActiveX control that provides the ability to view HTML help files. The HHCtrl Object is included in the file hhctrl.ocx and provides the ProgID (Programmatic Identifier) of Internet.HHCtrl. The HHCtrl Object fails to properly validate input.


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 MS07-008. This update provides a newer version of the HHCtrl Object.

Disable the HTML Help ActiveX control in Internet Explorer

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

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\{52a2aaae-085d-4187-97ea-8c30db990436}]
"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. 

Vendor Information


Microsoft Corporation Affected

Updated:  February 13, 2007



Vendor Statement

We have not received a statement from the vendor.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.


Please see Microsoft Security Bulletin MS07-008.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

CVSS Metrics

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This vulnerability was reported by Microsoft, who in turn credit HD Moore of BreakingPoint Systems.

This document was written by Will Dormann.

Other Information

CVE IDs: CVE-2007-0214
Severity Metric: 16.07
Date Public: 2007-02-13
Date First Published: 2007-02-13
Date Last Updated: 2007-02-23 13:42 UTC
Document Revision: 9

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