Kubernetes ClusterRoles that grant control over validating or mutating admission webhook configurati

Rule Details

Cortex AppSec Rule ID	APPSEC_K8S_155
Category - Subcategory	Kubernetes - Access Control
Provider	OTHER
Severity	HIGH
Framework	Helm, Kubernetes, Kustomize

Impact

ClusterRoles that grant write permissions over admission webhook should be minimized to reduce powerful identities in the cluster. Validating admission webhooks can read every object admitted to the cluster, while mutating admission webhooks can read and mutate every object admitted to the cluster. As such, ClusterRoles that grant control over admission webhooks are granting near cluster admin privileges. Minimize such ClusterRoles to limit the number of powerful credentials that if compromised could take over the entire cluster.

How to Fix

Kind: ClusterRole

• Arguments: rules ClusterRoles that grant the "create", "update" or "patch" verbs over the "mutatingwebhookconfigurations" or "validatingwebhookconfigurations" resources in the "admissionregistration.k8s.io" API group are granting control over admission webhooks. [source,go]

---

kind: ClusterRole apiVersion: rbac.authorization.k8s.io/v1 metadata: name: rules:

• apiGroups: [""] resources: ["pods"] verbs: ["get"]
• apiGroups: ["admissionregistration.k8s.io"] resources: ["mutatingwebhookconfigurations"] verbs:
• list

---