CIS-5.2.5 - Minimize the admission of containers wishing to share the host network namespace

Minimize the admission of containers wishing to share the host network namespace

Framework

CIS

Severity

Medium

Description of the the issue

A container running in the host's network namespace could access the local loopback device, and could access network traffic to and from other pods.

There should be at least one admission control policy defined which does not permit containers to share the host network namespace.

If you need to run containers which require access to the host's network namesapces, this should be defined in a separate policy and you should carefully check to ensure that only limited service accounts and users are given permission to use that policy.

Related resources

MutatingWebhookConfiguration, Namespace, ValidatingWebhookConfiguration

What does this control test

Do not generally permit containers to be run with the hostNetwork flag set to true.

How to check it manually

List the policies in use for each namespace in the cluster, ensure that each policy disallows the admission of hostNetwork containers

Remediation

Add policies to each namespace in the cluster which has user workloads to restrict the admission of hostNetwork containers.

Impact Statement

Pods defined with spec.hostNetwork: true will not be permitted unless they are run under a specific policy.

Default Value

By default, there are no restrictions on the creation of hostNetwork containers.

Example

No example