docker cold fusion 2018 cgi scope

You'll need to provide us more info. Many of the CGI vars (like that one) are actually controlled by the web server that fronts CF. What are you using?

By default, the CF Docker images run your traffic through the built-in web server within CF (port 8500). You may be using that (you'd know, based on whethr you exposed that port in your docker run or compose file, or other orchestration config).

Or you could well have implemented some web server like nginx or apache, or even IIS, whether within a container also or on your host (talking to the container).

Whichever web server you are using, you would then have to have enabled security for the web site in question, since you're expecting to see cgi.auth_user variable to be populated . What form of security did you enable in teh web server you're using? 

Or might it be that you did not enable any other web server, and are just using "the one in the CF docker image". In that case, it has no such web site security enabled, by default. So you should not expect to see that variable populated. If it's simply that it's blank, it should be, so you should change your code to work accordingly.

Or enable security within whichever web server you are using to talk to the CF container.

Let us know what you think.