ZPanel Code Execution

`Hi all,  
  
There's an arbitrary (PHP) code execution in ZPanel, a free and  
open-source shared hosting control panel. Using the included zsudo  
binary, access can be escalated and commands can be run as root.  
  
The vulnerability: ZPanel uses a poor "templater" system that  
basically consists of a few str_replace calls and an eval... and as  
could be expected from something like this, it does a very poor job at  
preventing malicious code. The relevant code can be seen here:  
https://github.com/bobsta63/zpanelx/blob/master/dryden/ui/templateparser.class.php  
(note the poor attempt at stripping out <?php and ?> tags).  
  
By effectively injecting the replacement that occurs in line 71, one  
can run arbitrary PHP code. When combined with ZPanels `zsudo` binary,  
one can execute arbitrary commands as root, with a maximum of 5  
additional arguments (aside from the path to the  
to-be-executed-command).  
  
The scope: Custom templates/themes can be uploaded by resellers and  
administrators. This effectively means that anyone that can get access  
to a reseller account through any means, including by purchasing a  
reseller service from a ZPanel-using host, can gain root access,  
without detection.  
  
PoC: Insert the following code anywhere in master.ztml or any other  
template that is parsed by the template parser, replacing `touch derp`  
with any command of choice:  
  
<& bogus']; exec("/etc/zpanel/panel/bin/zsudo touch /root/derp"); echo  
$value['bogus &>  
  
Strangely, login.ztml does not appear to use the templater, and seems  
to allow PHP execution by simply using <?php and ?> tags (which I  
would consider a vulnerability in itself, but that aside).  
  
Vendor notification: I have warned the ZPanel development team about  
their insecure templater *months* ago, and explicitly pointed out that  
their "PHP code filtering" was not going to work well. I have  
submitted a patch for some other fixable aspects of the templater  
(which was merged into the main repository), but the development team  
insisted that the security in the templater was fine, and that it  
wasn't a problem, basically telling me that they were not going to  
change it. They have not fixed this vulnerability, nor do they appear  
to have any interest in doing so in the near future.  
  
How to solve it: Either remove the reseller template uploading  
functionality (this would impair core functionality), or use a real  
templating engine that does not use a few str_replace() calls strung  
together in front of an eval().  
  
I'm quite new to this list, and not exactly a pentesting expert, so if  
I left out some important information in the above message, please do  
let me know.  
  
- Sven Slootweg  
  
  
`