------------------------------------------------------------------------- Tiki Wiki CMS Groupware <= 8.2 (snarf_ajax.php) Remote PHP Code Injection ------------------------------------------------------------------------- author...........: Egidio Romano aka EgiX mail.............: n0b0d13s[at]gmail[dot]com software link....: http://info.tiki.org/ [-] Vulnerability explanation: The vulnerable code is located into /lib/wiki-plugins/wikiplugin_snarf.php: 170. // If the user specified a more specialized regex 171. if ( isset($params['regex']) && isset($params['regexres']) && preg_match('/^(.)(.)+\1[^e]*$/', $params['regex']) ) { 172. $snarf = preg_replace( $params['regex'], $params['regexres'], $snarf ); 173. } input passed through $_REQUEST['regex'] is checked by a regular expression at line 171 to prevent execution of arbitrary PHP code using the 'e' modifier in a call to preg_replace() at line 172. But this check could be bypassed with a null byte injection, requesting an URL like this: http://<hostname>/tiki-8.2/snarf_ajax.php?url=1&regexres=phpinfo()&regex=//e%00/ Tiki internal filters remove all null bytes from user input, but for some strange reason this doesn't happen within admin sessions. So, successful exploitation of this vulnerability requires an user account with administration rights and 'PluginSnarf' to be enabled (not by default). [-] Disclosure timeline: [23/11/2011] - Vulnerability discovered [24/11/2011] - Issue reported to security(at)tikiwiki.org [24/11/2011] - New ticket opened: http://dev.tiki.org/item4059 [27/11/2011] - Vendor confirmed the issue [27/11/2011] - CVE number requested [28/11/2011] - Assigned CVE-2011-4558 [22/12/2011] - After four weeks still no fix released [23/12/2011] - Public disclosure