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