Secunia

A vulnerability has been identified in AOL Instant Messenger (AIM), which potentially can be exploited by malicious people to compromise a user's system.

The vulnerability is caused due to a boundary error in the "CCertsByUserName::Cleanup()" function in "AimSecondarySvcs.dll" when constructing certain error messages. The problem is that a "sprintf()" function is used insecurely when constructing an error message to inform the user that the connection with a specified user was unsuccessful.

This can be exploited via a user's browser by constructing a specially crafted link that uses the "aim:" URI handler and requests a "getfile" operation, which supplies an overly long, specially crafted string to the "screenname" parameter.

Example:
aim:getfile?screenname=AAA...[x1130]...AAA

Successful exploitation causes a buffer overflow and may potentially allow execution of arbitrary code. However, it requires the following:

1) A user has to be tricked into visiting a malicious website or clicking a specially crafted link.
2) The user clicks "OK" when an anti-virus warning dialog box pops up unless it has been disabled previously.

The vulnerability has been confirmed in version 5.2.3292 for Windows. However, other versions may also be affected.

Solution
The vulnerability has been fixed in the latest beta (version 5.5.3415 Beta).
Further details available in Customer Area

Provided and/or discovered by
AngryB, Digital Pranksters.

Original Advisory
Buffer Overflow in AOL Instant Messager's screenname parameter of getfile:
http://www.digitalpranksters.com/advisories/aol/AIMProtocolBO.html

Deep Links
Links available in Customer Area