C-0219 - Minimize the admission of containers with added capabilities

Framework

cis-aks-t1.2.0, cis-eks-t1.2.0

Severity

Medium

Description of the the issue

Containers run with a default set of capabilities as assigned by the Container Runtime. Capabilities outside this set can be added to containers which could expose them to risks of container breakout attacks.

There should be at least one PodSecurityPolicy (PSP) defined which prevents containers with capabilities beyond the default set from launching.

If you need to run containers with additional capabilities, this should be defined in a separate PSP and you should carefully check RBAC controls to ensure that only limited service accounts and users are given permission to access that PSP.

Related resources

PodSecurityPolicy

What does this control test

Do not generally permit containers with capabilities assigned beyond the default set.

How to check it manually

Get the set of PSPs with the following command:

kubectl get psp

Verify that there are no PSPs present which have allowedCapabilities set to anything other than an empty array.

Remediation

Ensure that allowedCapabilities is not present in PSPs for the cluster unless it is set to an empty array.

Impact Statement

Pods with containers which require capabilities outwith the default set will not be permitted.

Default Value

By default, PodSecurityPolicies are not defined. If a PSP is created 'allowedCapabilities' is set by default.

Example

No example