A new vulnerability CVE-2018-19788 has been discovered on Linux systems which effects on major Linux OS products including Red Hat, Debian, Ubuntu, and Cent OS. This vulnerability can be very easily exploited on Linux systems.
Vulnerability Summary: A low privilege user on most Linux systems with uid greater than 2147483647 automatically gets the system level privilege for issuing system level systemctl command.
A word about Polkit (formerly PolicyKit): Polkit is a component for controlling system-wide privileges in Unix-like operating systems. It provides an organized way for non-privileged processes to communicate with privileged ones. Polkit allows a level of control of centralized system policy.