TITLE:
AOL Instant Messenger File Transfer Error Message Buffer Overflow
Vulnerability

SECUNIA ADVISORY ID:
SA10021

VERIFY ADVISORY:
http://www.secunia.com/advisories/10021/

CRITICAL:
Moderately critical

IMPACT:
DoS, System access

WHERE:
From remote

SOFTWARE:
AOL Instant Messenger 5.x

DESCRIPTION:
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).
http://www.aim.com/get_aim/win/win_beta.adp

REPORTED BY / CREDITS:
AngryB, Digital Pranksters.

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

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