Vulnerability Note VU#949817

Yahoo! Webcam image upload ActiveX control vulnerable to arbitrary code execution

Overview

The Yahoo! Webcam image upload ActiveX control contains a stack buffer overflow, which can allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system.

I. Description

Yahoo! Webcam is a component of Yahoo! Messenger that allows users to chat via webcams over a network. Yahoo! Webcam Upload includes an ActiveX control provided by the file ywcupl.dll . This ActiveX control contains a stack buffer overflow vulnerability in the Server property.

We are aware of publicly available exploit code for this vulnerability.

II. Impact

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.

III. Solution

Apply an update

This issue is addressed in Yahoo! Messenger 8.1. If you are unable to upgrade, please consider the following workarounds:

Disable the Yahoo! Messenger ActiveX control in Internet Explorer

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

(DCE2F8B1-A520-11D4-8FD0-00D0B7730277)

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_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX Compatibility{DCE2F8B1-A520-11D4-8FD0-00D0B7730277}]
"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

Vendor	Status	Date Updated
Yahoo, Inc.	Vulnerable	8-Jun-2007

References

http://research.eeye.com/html/alerts/zeroday/20070606.html
http://secunia.com/advisories/25547/
http://messenger.yahoo.com/security_update.php?id=060707

Credit

This issue was reported by eEye Digital Security in EEYEZD-20070606.

This document was written by Chris Taschner.

Other Information

Date Public	06/07/2007
Date First Published	06/08/2007 11:58:12 AM
Date Last Updated	06/11/2007
CERT Advisory
CVE Name
Metric	15.53
Document Revision	20