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Aol Instant Messenger DoS vulnerability

daemon@ATHENA.MIT.EDU (hi im cruz)
Fri Mar 3 16:18:19 2000

Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Message-Id:  <20000303154750.23363.qmail@hotmail.com>
Date:         Fri, 3 Mar 2000 07:47:50 PST
Reply-To: hi im cruz <justcruzn@HOTMAIL.COM>
From: hi im cruz <justcruzn@HOTMAIL.COM>
X-To:         BUGTRAQ@SECURITYFOCUS.COM
To: BUGTRAQ@SECURITYFOCUS.COM

As all Ascii-Symbols can be displayed in &#XXX; format, where XXX are
numbers from 0-255, AIM seems not to check the XXX for higher values
and some strings above 255 result in aim crashing completly or in part.

E.g. the string &#770; will result in crashing the whole aim, but &#771;
will crash only the instant message window (&#771; was only tested once
by me).
It will crash the AIM of the attacker too, because AIM displays the string
in the attacker-Instant Message, so the attacker-AIM also tries to convert
it and errors.

There is already an unofficial fix available, which can be downloaded at my
hompage: http://laugh.at/cruz
The fix is an edited ate32.dll, which should be copied to the aim directory.
With it, aim doesnt try to convert "&#XXX;"-type of strings anymore, a
minimum drawback (note: with that fix, the attacker can use this exploit to
crash other unfixed AIMs, but wont crash his/her own AIM).

Affected versions: I tested this only on 3.5+ versions of AIM, but all other
versions are most likely affected too.

-cruz
http://laugh.at/cruz

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