Public Vulnerability Reports

Yahoo Messenger YMailAttach ActiveX Control Heap Corruption Vulnerability



Yahoo Messenger is a instant messaging application that allows users to chat online, share files, conduct PC to PC calls and more. More information can be found on the vendors site at:


Remote exploitation of a heap corruption vulnerability in Yahoo Inc.'s Yahoo! Messenger could allow malicious web sites to execute arbitrary code with the privileges of the currently logged in user.

The vulnerability specifically lays with in the following ActiveX Control:

ProgID: YMMAPI.YMailAttach
Clsid: AA218328-0EA8-4D70-8972-E987A9190FF4
File: C:PROGRA~1YAHOO!COMMONymmapi.dll
Version: 2004.11.23.1

The overflow is triggered by setting the TextETACalculating property to an overly long string.


This vulnerability can be triggered by a malicious website. Users would be required to have a vulnerable version of the target software installed and be lured to a malicious site.


iDefense has confirmed the existence of this vulnerability in version 8.0 of Yahoo Instant Messenger. Version 7.5 has also been reported vulnerable. Previous versions are suspected vulnerable as well.


Users can set the kill bit for the target ActiveX control to block the control from loading within Internet Explorer.


Yahoo has addressed this vulnerability within version 2005.1.1.4 of their Messenger product. This version sets the kill bit for the affected control. More information can be found at the link shown below.


The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2006-6603 to this issue. This is a candidate for inclusion in the CVE list ( which standardizes names for security problems.


10/26/2006 Initial vendor notification
12/15/2006 Initial vendor response
12/15/2006 Coordinated public disclosure


This vulnerability was reported to iDefense by Peter Vreugdenhil.

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Copyright © 2006 Verisign, Inc.

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