Joomla! Component Community Builder Enhanced (CBE) 1.4.8/1.4.9/1.4.10 – Local File Inclusion / Remote Code Execution
Description: Joomla CBE suffers from a local file inclusion vulnerability. As CBE also offers file uploading functionality that allows to upload files that contain php-code, this can be used to execute arbitary system-commands on the host with the webservers privileges. Risk: High Affected versions: - CBE v1.4.10 - CBE v1.4.9 - CBE v1.4.8 (maybe older versions) Not affaceted: - CBE v1.4.11 (current) Vulnerable code: in cbe.php a file identified by the param "tabname" is included if the "ajaxdirekt" param is set, without sanatizing the value of "tabname" first: -- $ajaxdirekt = JRequest::getVar('ajaxdirekt', null); $tabname = JRequest::getVar('tabname', null); if ($ajaxdirekt) { $tabfile = JPATH_SITE.DS.'components'.DS.'com_cbe'.DS.'enhanced'.DS.$tabname.DS.$tabname.".php"; if (file_exists($tabfile)) { include_once($tabfile); } return; } -- Exploitation / poc: index.php?option=com_cbe&task=userProfile&user=23&ajaxdirekt=true&tabname=../../../CREDITS.php%00 will execute the CREDITS.php Addional attack-vectors: CBE offers a file-upload function for uploading user profile images. The uploaded file is not checked for beeing well-formed, it only needs to have the right mime-type and maybe (depends on profile-picture configuration) the right size, so we can embed php-code in the profile-picture. Lets say we have registered an account on the site with the user-id 23, then we can execute the backdoor by requesting: index.php?option=com_cbe&task=userProfile&user=23&ajaxdirekt=true&tabname=../../../images/cbe/23.gif%00 As we stay in the documents-root, we dont even have to worry about safe-mode directory restrictions, and using GIFs will bypass most of CBE's image pre-processing functions during file upload (except file- and image-size checks). Solutions: a) check if the contents of an uploaded file contains a php open-tag ('<?php') (requires that the php-short-open-tag option is disabled) b) Joomla offers several functions for accessing POST and GET params, i guess using getWord() instead of getVar() would be a better choice in this case. History: 04.10.2010 - vendor informed 07.10.2010 - vendor released fixed version 08.10.2010 - public disclosure Cheers Delf Tonder |