search menu icon-carat-right cmu-wordmark

CERT Coordination Center

HHOpen ActiveX Control buffer overflow in OpenHelp method

Vulnerability Note VU#29795

Original Release Date: 2000-10-31 | Last Revised: 2000-11-01



The HHOpen ActiveX control (hhopen.ocx) has a buffer overflow in the OpenHelp method. Because the control is marked safe-for-scripting, an attacker may be able to script this control and exploit the vulnerability when you visit a web page.

The classID for the vulnerable control is: {130D7743-5F5A-11D1-B676-00A0C9697233}.


An attacker may be able to exploit a buffer overflow in the HHOpen ActiveX control and execute arbitrary code on the system of the person visiting a malicious web page.


Apply a patch

Apply the patch provided by Microsoft in Security Bulletin MS99-037. This patch sets the kill bit which prevents the control from being loaded by Internet Explorer.

Disable "Script ActiveX controls marked safe for scripting"

In your Internet Explorer security settings, set this option to "disable" or "prompt".

Vendor Information

Affected   Unknown   Unaffected


Updated:  October 31, 2000



Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

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


The CERT/CC has no additional comments at this time.

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

CVSS Metrics

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



This document was written by Cory F Cohen.

Other Information

CVE IDs: None
Severity Metric: 12.66
Date Public: 1999-09-10
Date First Published: 2000-10-31
Date Last Updated: 2000-11-01 15:08 UTC
Document Revision: 8

Sponsored by the Department of Homeland Security Office of Cybersecurity and Communications.