AOL AIM and ICQ File Transfer Path-Traversal Vulnerability
iDefense Security Advisory 04.09.07
Apr 09, 2007
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/
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.
Exploitation of this vulnerability allows attackers to place arbitrarily
named files in a directory of their choice when the victim accepts a
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.
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
iDefense is currently unaware of any effective workaround for this
VI. VENDOR RESPONSE
AOL has provided the following solutions to address this vulnerability.
"1. Active ICQ clients have already been patched via an automatic
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
The discoverer of this vulnerability wishes to remain anonymous.
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X. LEGAL NOTICES
Copyright =A9 2007 iDefense, Inc.
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