Advisory CA-2002-16 Multiple Vulnerabilities in Yahoo! Messenger

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CERT Advisory CA-2002-16 Multiple Vulnerabilities in Yahoo! Messenger

Original release date: June 05, 2002
Last revised: –
Source: CERT/CC

A complete revision history can be found at the end of this file.

Systems Affected

 * Yahoo!  Messenger  version  5,0,0,1064  and  prior  for  Microsoft
   Windows

Overview

There are multiple vulnerabilities in Yahoo! Messenger. Attackers that
are able to exploit these vulnerabilities may be able to execute
arbitrary code with the privileges of the victim user. We have not
seen active scanning for these vulnerabilities, nor have we received
any reports of these vulnerabilities being exploited, but users should
upgrade to version 5,0,0,1065 or later.

I. Description

Yahoo! Messenger is a widely used program for communicating with other
users over the Internet. On May 27, 2002, a buffer overflow and a URL
validation vulnerability were discovered in the Yahoo! Messenger
client for Microsoft Windows. Details of each vulnerability follow:

 VU#137115  - Yahoo! Messenger contains a buffer overflow in the URI
 handler

 The  buffer  overflow  occurs  during  the processing of the Yahoo!
 Messenger  URI  handler  (ymsgr:). This URI handler is installed at
 the system level for applications that use the underlying operating
 system when processesing URIs (such as Microsoft Internet Explorer,
 Netscape  Navigator  6, Microsoft Outlook, or the command shell). A
 URI  can  be  sent  by  another Yahoo! Messenger user in a message,
 embedded  in  a  web  site,  or  sent  in  an HTML-renderable email
 message.

 This vulnerability has been assigned as CAN-2002-0031 by the Common
 Vulnerabilities and Exposures (CVE) group:

 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-0031

 VU#172315  -  Yahoo!  Messenger  "addview"  function allows for the
 automatic execution of malicious script contained in web pages

 A  vulnerability  exists in the Yahoo! Messenger "addview" function
 that permits a remote attacker to execute arbitrary script and HTML
 in  the  Internet security zone of the local machine. The "addview"
 function  is  only  supposed to accept view information from Yahoo!
 servers. However, an attacker can send malicious script and HTML to
 the client using the Yahoo! URL redirection service. This script or
 HTML is interpreted by the Yahoo! Messenger client and is displayed
 in the client's web browser.

 This vulnerability has been assigned as CAN-2002-0032 by the Common
 Vulnerabilities and Exposures (CVE) group:

 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-0032

These vulnerabilities were resolved in Yahoo! Messenger version
5,0,0,1065, released May 22, 2002; however, a bug in the distribution
server may have inadvertantly installed Yahoo! Messenger version
5,0,0,1036 on systems that downloaded Yahoo! Messenger after May 22,
2002. The bug in the distribution server has since been resolved.

In February 2002, the following vulnerabilities were reported to
affect Yahoo! Messenger:

 * http://www.kb.cert.org/vuls/id/393195
 * http://www.kb.cert.org/vuls/id/419419
 * http://www.kb.cert.org/vuls/id/755755
 * http://www.kb.cert.org/vuls/id/887319
 * http://www.kb.cert.org/vuls/id/952875

All of these vulnerabilities were resolved in Yahoo! Messenger version
5,0,0,1058, released February 25, 2002, or by server-side resolutions
around the same time.

II. Impact

A remote attacker can execute arbitrary code with the privileges of
the victim user, cause a denial of service, or modify data in the
victim's buddy list.

III. Solution

Upgrade to the latest version of Yahoo! Messenger

 On  May  22,  2002,  Yahoo!  released  a  fixed  version  of Yahoo!
 Messenger  (5,0,0,1065)  and began issuing a patch (5,0,0,1066) via
 the  AutoUpdater to address this issue. All users should upgrade to
 version   5,0,0,1065   or  later.  Users  with  versions  prior  to
 5,0,0,1066  that  have "Auto Update" enabled will receive a message
 informing  them  that  an  upgrade  is  available. All users should
 accept this upgrade.

 Users who downloaded Yahoo! Messenger after May 22, 2002, should be
 aware  that a bug in the distribution server may have inadvertantly
 installed  Yahoo! Messenger version 5,0,0,1036, which is vulnerable
 to  all issues in this advisory. The bug in the distribution server
 has since been resolved.

 Users  should upgrade and verify the version of Yahoo! Messenger by
 selecting  the  "About  Yahoo!  Messenger..."  option from the Help
 menu.

Implement a firewall and filtering

 Yahoo! Messenger listens for peer-to-peer requests on port 5101/TCP
 but  users  can  implement a firewall to block inbound and outbound
 access  to port 5101/TCP. However, since Yahoo! Messenger URI's can
 be  embedded  in  a web site or email message, blocking requests to
 and from port 5101/TCP is not a completely effective solution. Mail
 and  Internet filters should also be applied to filter the "ymsgr:"
 URI handler from email messages and web sites.

Appendix A. - Vendor Information

This appendix contains information provided by vendors for this
advisory. When vendors report new information to the CERT/CC, we
update this section and note the changes in our revision history. If a
particular vendor is not listed below, we have not received their
comments.

Yahoo!, Inc.

 Yahoo!  encourages  users to upgrade to the latest version whenever
 prompted by the AutoUpdater or regularly check for updated versions
 of the client at http://messenger.yahoo.com.
 _________________________________________________________________

The CERT Coordination Center thanks Scott Woodward
<[email protected]>, Phuong Nguyen <[email protected]>, and Adam
Lang <[email protected]> for their discovery and analysis of these
vulnerabilities. We also thank Yahoo! for their assistance in
analyzing and responding to these issues.
_________________________________________________________________

Feedback can be directed to the author: Jason A. Rafail
_________________________________________________________________

Appendix B. - References

1. http://www.kb.cert.org/vuls/id/137115
2. http://www.kb.cert.org/vuls/id/172315
3. http://www.kb.cert.org/vuls/id/393195
4. http://www.kb.cert.org/vuls/id/419419
5. http://www.kb.cert.org/vuls/id/755755
6. http://www.kb.cert.org/vuls/id/887319
7. http://www.kb.cert.org/vuls/id/952875

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http://www.cert.org/advisories/CA-2002-16.html

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Revision History
June 05, 2002: Initial release

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