Docker internally uses an api to communicate between docker client (eg. docker command) and docker daemon.
If you have access to this docker socket, you effectively have root access to the docker host. This is mentioned in the documentation, but hell, I was suprised it was that easy.
Try this on your local docker machine:
docker run -it --mount type=bind,src=/,destination=/host debian:latest sh
This will give you shell that has your root folder mounted on /host directory with full read and write root access to the file system.
In other words: If you can run docker from local user, you don't need to ask password for sudo.