‘PHP Globals Filtering Bypass’


Improper global parameters handling within PHP allows attackers to overwrite existing data.’


‘The information has been provided by ascii.
The original article can be found at: http://www.ush.it/2006/01/25/php5-globals-vulnerability/


Vulnerable Systems:
 * PHP version 4.3.10 and prior
 * PHP version 5.0.5 and prior
 * PHP version 5.1.1
 * PHP version 5.1.2

By using a global variable in PHP attackers can overwrite the content with it’s own as following:

Proof of Concept:
< ? echo $foobar; ? >

On address bar do the following:


If the poc prints out HELLO your PHP version is vulnerable.

Please note that the PHP globals must be on in order to be vulnerable.

Register global off will fix. This PHP code will mitigate this bug.

// put this code before everything
if (isset($HTTP_POST_VARS[‘GLOBALS’]) || isset($_POST[‘GLOBALS’]) ||
    isset($HTTP_POST_FILES[‘GLOBALS’]) || isset($_FILES[‘GLOBALS’]) ||
    isset($HTTP_GET_VARS[‘GLOBALS’]) || isset($_GET[‘GLOBALS’]) ||
    isset($HTTP_COOKIE_VARS[‘GLOBALS’]) || isset($_COOKIE[‘GLOBALS’])) {
 trigger_error(‘Is this a GLOBAL GPC hacking attemp?’, E_USER_ERROR);

Disclosure Timeline:
20060119 Bug discovered
20060119 Internal release
20060125 Initial release (only on ush.it)
20060127 Initial release (only on sikurezza.org)
20060128 Public release’

Categories: UNIX