GHSA-g2j9-g8r5-rg82

Summary

An unauthenticated Local File Inclusion exists in the template-switching feature: if templateselection is enabled in the configuration, the server trusts the template cookie and includes the referenced PHP file. An attacker can read sensitive data or, if they manage to drop a PHP file elsewhere, gain RCE.

Affected versions

PrivateBin versions since 1.7.7.

Conditions

• templateselection got enabled in cfg/conf.php
• Visitor sets a cookie template pointing to an existing PHP file without it's suffix, using a path relative to the tpl folder. Absolute paths do not work.

Impact

The constructed path of the template file is checked for existence, then included. For PrivateBin project files this does not leak any secrets due to data files being created with PHP code that prevents execution, but if a configuration file without that line got created or the visitor figures out the relative path to a PHP script that directly performs an action without appropriate privilege checking, those might execute or leak information.

Impact analysis

In detail, we have analyzed different ways of exploiting this vulnerability and found no way to cause a full remote code execution (RCE) vulnerability or denial of service (DoS) as recursive includes, e.g., are not possible.

Generally, it is again notably to remember only PHP files of the local filesystem can be included. That's why potentially at risk PrivateBin PHP files have been analyzed.

• the PrivateBin config file is by default protected as it prevents access itself resulting in a 403 HTTP status code. This is called the “(PHP) protection line”.
• Likewise, the paste data cannot be accessed due to that “protection line”. [Each created file contains the same line protecting it...