cis-k8s-v1111-1-2-9

name	cis-k8s-v1111-1.2.9
description	Ensure that the admission control plugin EventRateLimit is set (Manual)
category	cis-k8s
version	1.11.1
author	cyberstrike-official
tags	["cis","kubernetes","control-plane","api-server","admission-control","rate-limiting"]
cis_id	1.2.9
cis_benchmark	CIS Kubernetes Benchmark v1.11.1
tech_stack	["kubernetes"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

1.2.9 Ensure that the admission control plugin EventRateLimit is set (Manual)

Profile Applicability

• Level 1 - Master Node

Description

Limit the rate at which the API server accepts requests.

Rationale

Using EventRateLimit admission control enforces a limit on the number of events that the API Server will accept in a given time slice. A misbehaving workload could overwhelm and DoS the API Server, making it unavailable. This particularly applies to a multi-tenant cluster, where there might be a small percentage of misbehaving tenants which could have a significant impact on the performance of the cluster overall. Hence, it is recommended to limit the rate of events that the API server will accept.

Impact

You need to carefully tune in limits as per your environment.

Audit

Run the following command on the Control Plane node:

ps -ef | grep kube-apiserver

Verify that the --enable-admission-plugins argument is set to a value that includes EventRateLimit.

Remediation

Follow the Kubernetes documentation and set the desired limits in a configuration file. Then, edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml and set the below parameters.

--enable-admission-plugins=...,EventRateLimit,...
--admission-control-config-file=<path/to/configuration/file>

Default Value

By default, EventRateLimit is not set.

References

1. https://kubernetes.io/docs/reference/command-line-tools-reference/kube-apiserver/
2. https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#eventratelimit
3. https://github.com/staebler/community/blob/9873b632f4d99b5d99c38c9b15fe2f8b93d0a746/contributors/design-proposals/admission_control_event_rate_limit.md

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	16.11 Leverage Vetted Modules or Services for Application Security Components