Re: ICQ remote buffer overflow vulnerability

[Daniel Tan <datan () seas upenn edu>]

I've discovered that the same payload can be sent through Direct 
Connection with the receiver, even with the DC settings set to 
maximum (ie. allow only users on my contact list, allow DC 
upon authorisation, do not allow older version of clients to DC).
If the sender is 'trusted' (ie. on the users' contact list), the
sender can establish a TCP connection with the users' listening
port even if DC settings are on maximum (in which case the 
receiver's IP & port are not given to the sender, but one can
find this out in other ways eg. email header + port scan).


Whereas having the payload sent through the server allows a 
possible remedy in having the server check for malformed packets, 
being able to send the packet directly to the client takes away
that possibility. 

Again, this works only for ICQ2000 clients.


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Daniel Tan
Class of 2004
Jerome Fisher Management & Technology Program
University of Pennsylvania, USA
datan () seas upenn edu
datan () wharton upenn edu
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