Lynis is an open source security auditing tool. Lynis is light-weight and easy to use.
Although Lynis is available in most of Linux package managers - its installation is not required, as it written in shell script.
Download script (clone from github):
git clone https://github.com/CISOfy/lynis
Go to cloned directory:
cd lynis/
./lynis audit system
lynis audit dockerfile <path/to/docker>