For those of you who have a desire to crash Microsoft's PPTP stack, I have a pptp .spk script linked off of http://www.immunitysec.com/spike.html.
It would probably be good to run against other PPTP stacks as well. (Likewise, SPIKE's msrpcfuzzer takes down free software dce-rpc stacks just as fast as it takes down the non-free stacks.)
It's not a bad demonstration of how to use SPIKE scripts either, if you're inclined to learn. Finding this bug took less than thirty minutes...(</marketing>)
To run it:
bash$ . ./ls.sh
machine. It's a good idea to set up SoftIce as well. bash$ ./generic_send_tcp 192.168.1.100 1723 ./pptp.spk 0 0
Dave Aitel Immunity, Inc.
 phion Information Technologies http://www.phion.com/
phion Information Technologies will not provide an exploit for this issue.