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.
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 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.
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.
iDefense is currently unaware of any effective workaround for this issue.
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."
A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet.
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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Copyright © 2007 Verisign, Inc.
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