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             AUSCERT External Security Bulletin Redistribution

                          ESB-2007.0238 -- [Win]
        AOL AIM and ICQ File Transfer Path-Traversal Vulnerability
                               11 April 2007

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:              AIM 5.9 and prior
                      ICQ 5.1 and prior
Publisher:            iDefense
Operating System:     Windows
Impact:               Create Arbitrary Files
Access:               Remote/Unauthenticated

Original Bulletin:    
  http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=508

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AOL AIM and ICQ File Transfer Path-Traversal Vulnerability

iDefense Security Advisory 04.09.07
http://labs.idefense.com/intelligence/vulnerabilities/
Apr 09, 2007

I. BACKGROUND

AOL Instant Messenger and ICQ are instant messaging applications that
allow users to exchange messages and files. More information can be
found on the vendor's site at the following URLs.

http://www.aim.com/ or http://www.icq.com/

II. DESCRIPTION

Remote exploitation of a path-traversal vulnerability in AOL's AIM and
ICQ could allow a remote attacker to place arbitrary files on the
victim's machine during a file transfer operation.

AIM and ICQ allow users to share and transfer files via a custom
protocol. During file transfers, the sender is allowed to specify the
display name of the file, and the filename used for the transfer.

The recipient can only specify the folder in which to save the file. Due
to an input validation flaw, the clients do not properly strip "../"
traversal characters from the filename the attacker supplies. By
specially encoding the path attackers can force the file to be saved to
a directory of their choosing when the victim accepts the file transfer.

III. ANALYSIS

Exploitation of this vulnerability allows attackers to place arbitrarily
named files in a directory of their choice when the victim accepts a
file transfer.

By default ICQ warns users that file transfers are unsafe and to only
accept file transfers from trusted users. ICQ also requires that a user
is on your contact list in order to accept a file transfer. Users must
manually accept the file transfer in order to be exploited.

During the file download, the traversal path is displayed in the
filename portion of the dialog. ICQ will not overwrite existing files
without prompting the user for confirmation. It is important to note
that the attacker specifies the display name used in the file accept
dialog. This file name is arbitrary and need not be the same as the
actual file being transferred.

IV. DETECTION

iDefense has confirmed this vulnerability in ICQ version 5.1. Previous
versions are suspected vulnerable.

Additionally, AOL reported that AIM version 5.9 and prior are
vulnerable.

V. WORKAROUND

iDefense is currently unaware of any effective workaround for this
issue.

VI. VENDOR RESPONSE

AOL has provided the following solutions to address this vulnerability.

"1. Active ICQ clients have already been patched via an automatic
update.

2. Users of the AIM client 5.9 and earlier are urged to upgrade to the
latest version of the AIM client from http://www.aim.com/.

3. In addition, AIM 5.9 users are also protected by a fix that has been
applied to the AIM infrastructure."

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

02/01/2007  Initial vendor notification
02/01/2007  Initial vendor response
04/09/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research
http://labs.idefense.com/methodology/vulnerability/vcp.php

Free tools, research and upcoming events
http://labs.idefense.com/

X. LEGAL NOTICES

Copyright © 2007 iDefense, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDefense. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically,
please e-mail customerservice@idefense.com for permission.

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
author nor the publisher accepts any liability for any direct,
indirect, or consequential loss or damage arising from use of, or
reliance on, this information.

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