Vulnerability Note VU#563756

Microsoft HTML Help ActiveX control fails to properly validate input

Original Release date: 13 Feb 2007 | Last revised: 23 Feb 2007


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 This update provides a newer version of the HHCtrl Object.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. 

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
Microsoft CorporationAffected-13 Feb 2007
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



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
  • Date Public: 13 Feb 2007
  • Date First Published: 13 Feb 2007
  • Date Last Updated: 23 Feb 2007
  • Severity Metric: 16.07
  • Document Revision: 8


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