search menu icon-carat-right cmu-wordmark

CERT Coordination Center

Yahoo Messenger YMailAttach ActiveX control buffer overflow

Vulnerability Note VU#901852

Original Release Date: 2006-12-15 | Last Revised: 2007-02-06


The Yahoo Messenger YMailAttach ActiveX control contains a buffer overflow, which could allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.


Yahoo Messenger is an instant messaging application. Yahoo Messenger includes several ActiveX controls. The YMailAttach ActiveX control, which is provided by ymmapi.dll, contains a buffer overflow vulnerability.


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.


Apply an update

As specified in the Yahoo Security Update, this issue is addressed in versions of Yahoo Messenger from Nov 2nd 2006 or later. Version 2005.1.1.4 or higher of ymmapi.dll contains the fix.

Disable the YMailAttach ActiveX control in Internet Explorer

The Yahoo YMailAttach 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\{AA218328-0EA8-4D70-8972-E987A9190FF4}]
"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


Yahoo, Inc. Affected

Updated:  December 15, 2006



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 the Yahoo Security Update.

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

CVSS Metrics

Group Score Vector



Thanks to Yahoo for reporting this vulnerability.

This document was written by Will Dormann.

Other Information

CVE IDs: CVE-2006-6603
Severity Metric: 27.95
Date Public: 2006-12-08
Date First Published: 2006-12-15
Date Last Updated: 2007-02-06 20:59 UTC
Document Revision: 9

Sponsored by CISA.