cis-k8s-v1110-4-2-15

name	cis-k8s-v1110-4.2.15
description	Ensure that the --IPAddressDeny is set to any (Manual)
category	cis-k8s
version	1.11.0
author	cyberstrike-official
tags	["cis","kubernetes","worker-node","kubelet","ip-address-deny","network-security","ip-filtering"]
cis_id	4.2.15
cis_benchmark	CIS Kubernetes Benchmark v1.11.0
tech_stack	["kubernetes"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

4.2.15 Ensure that the --IPAddressDeny is set to any (Manual)

Profile Applicability

• Level 2 - Worker Node

Description

Ensuring that --IPAddressDeny is set to "Any" will facilitate allowlisting of only IP addresses that are explicitly set with the --IPAddressAllow parameter which will block unspecified IP addresses from communicating with the kubelet component.

Rationale

By default, Kubernetes allows any IP address to communicate with the kubelet component IP restrictions and IP whitelisting are security best practices and reduce the attack surface of the kubelet.

Impact

Configuring the setting IPAddressDeny=any will deny service to any IP address not specified in the complimentary setting IPAddressDeny=any configuration parameter. Applying IPAddressDeny=any alone will completely disable communication with the component.

Audit

Review the Kubelet's start-up parameters for the value of --IPAddressDeny, and check the Kubelet configuration file for IPAddressDeny=any. If this entry is present it should be accompanied by IPAddressAllow={{ kubelet_secure_addresses }} to allow the control plane to communicate with the component.

Remediation

IPAddressDeny=any
IPAddressAllow={{ kubelet_secure_addresses }}

*Note kubelet_secure_addresses: "localhost link-local {{ kube_pods_subnets | regex_replace(',', ' ') }} {{ kube_node_addresses }} {{ loadbalancer_apiserver.address | default("") }}"

Default Value

By default IPAddressDeny is not enabled.

References

1. https://github.com/kubernetes-sigs/kubespray/pull/9194/files
2. https://kubernetes.io/docs/concepts/services-networking/network-policies/

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	2.5 Allowlist Authorized Software		x	x
v8	2.7 Allowlist Authorized Scripts			x
v7	2.7 Utilize Application Whitelisting