This document covers a vulnerability in policy kit (polkit) used on many Linux distributions, which enables an unprivileged local user to get a privileged shell (root) on the system by manually sending dbus messages to the dbus-daemon, then killing the request before it has been fully processed.
You can download it from the following link: https://packetstormsecurity.com/files/download/165230/Polkit-CVE-2021-3560.pdf
Source: https://packetstormsecurity.com/files/165230/Polkit-CVE-2021-3560-Research.html