An additional option is to use [Clair][1].


> Clair is an open source project for the static analysis of
> vulnerabilities in application containers (currently including appc
> and docker).
> 
>     In regular intervals, Clair ingests vulnerability metadata from a configured set of sources and stores it in the database.
>     Clients use the Clair API to index their container images; this creates a list of features present in the image and stores them in the
> database.
>     Clients use the Clair API to query the database for vulnerabilities of a particular image; correlating vulnerabilities and
> features is done for each request, avoiding the need to rescan images.
>     When updates to vulnerability metadata occur, a notification can be sent to alert systems that a change has occured.
> 
> Our goal is to enable a more transparent view of the security of
> container-based infrastructure. Thus, the project was named Clair
> after the French term which translates to clear, bright, transparent.


  [1]: https://github.com/coreos/clair