ZPanel – ‘templateparser.class.php’ Crafted Template Remote Command 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 <code>zsudo</code> 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 <code>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