I needed to patch my LabKey Server docker image on hosted Docker Hub for the ShellShock bug. To do this I ran the following:

Create a container using the image I want to update. This command will start a new container, using the docker image and then connect to it for interactive session (ie shell prompt).

docker run -t -i bconn/labkey-standalone /bin/bash

Now we can install the bash update

apt-get update
apt-get install --only-upgrade bash
exit 

Commit the changes in the container to the image

docker commit -m="Installed Bash update for ShellShock" -a="bconn" d22ec3cf6c8c bconn/labkey-standalone

Push the updated image to Docker Hub

docker push bconn/labkey-standalone

IMPORTANT: If you build a new image from the Dockerfile, it will be patched automatically during build process, as the Dockerfile contains the line from ubuntu:14.04. And the ubuntu 14.04 base image has been patched for ShellShock.

Update 10/10/2014: After a little more research, it looks like there is an additional(and probably better way) to update an image hosted on Docker Hub. That process is to build a clean, new image from the Dockerfile.

For example, using a clean docker session (ie no existing containers or images), I would have followed the instructions in the Usage section at https://github.com/LabKey/samples/blob/master/docker/labkey-standalone/README.md.

Then I would have pushed the newly created image to Docker Hub by running

 docker push bconn/labkey-standalone