Control: 5.21 Ensure that the host's UTS namespace is not shared

Description

UTS namespaces provide isolation between two system identifiers: the hostname and the NIS domain name. It is used to set the hostname and the domain which are visible to running processes in that namespace. Processes running within containers do not typically require to know either the hostname or the domain name. The UTS namespace should therefore not be shared with the host.

Sharing the UTS namespace with the host provides full permission for each container to change the hostname of the host. This is not in line with good security practice and should not be permitted.

Remediation

You should not start a container with the --uts=host argument. For example, do not start a container using the command below:

docker run --rm --interactive --tty --uts=host rhel7.2

Default Value

By default, all containers have the UTS namespace enabled and the host UTS namespace is not shared with any containers.