Yahoo Messenger YVerInfo.dll ActiveX Multiple Remote Buffer Overflow
Vulnerabilities

iDefense Security Advisory 08.30.07
http://labs.idefense.com/intelligence/vulnerabilities/
Aug 30, 2007

I. BACKGROUND

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 vendor's site at the following URL.

http://messenger.yahoo.com/

II. DESCRIPTION

Remote exploitation of multiple buffer overflow vulnerabilities in Yahoo
Inc.'s Yahoo! Messenger 8.1 allows attackers to execute arbitrary code
with the privileges of the currently logged in user.

When Yahoo Messenger 8.1 is installed, the following vulnerable ActiveX
Control is registered on the system.

  ProgID: YVerInfo.GetInfo.1
  Clsid: D5184A39-CBDF-4A4F-AC1A-7A45A852C883
  File: C:\Program Files\Yahoo!\Common\YVerInfo.dll
  Version: 2006.8.24.1

Stack based buffer overflows can be triggered through either the fvCom()
or info() methods of this class.

III. ANALYSIS

Exploitation allows attackers to execute arbitrary code with the
privileges of the currently logged in user. Users would be required to
have a vulnerable version of the target software installed and be lured
to a malicious site.

It is important to note that functions within this class can only be
called if the control believes it is being run from the yahoo.com
domain. In order for this exploit to be triggered an attacker would
either have to leverage a Cross-Site Scripting vulnerability in the
yahoo.com domain, or be able to control the targeted user's DNS
resolution for the domain.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in version
8.1 of Yahoo Instant Messenger. Previous versions are suspected to be
vulnerable as well.

V. WORKAROUND

Setting the kill bit for the vulnerable ActiveX control's CLSID will
prevent these issues from be exploited within Internet Explorer.

VI. VENDOR RESPONSE

Yahoo Inc. has addressed these vulnerabilities by releasing an updated
version of Yahoo! Messenger. More information is available at the
following URL.

http://messenger.yahoo.com/security_update.php?id=082907

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-4515 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

08/21/2007  Initial vendor notification
08/21/2007  Initial vendor response
08/30/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2007 iDefense, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
 There are no warranties with regard to this information. Neither the
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