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EUVD-2026-323824

fkie_cve-2026-22872

Capsule is a multi-tenancy and policy-based framework for Kubernetes. The Capsule Controller runs with cluster-admin privileges. Although the TenantResource RawItems processing logic forcibly sets the namespace, this is ineffective for cluster-scoped resources. Prior to version 0.13.0, tenant administrators can leverage the Controller's elevated privileges to create cluster-scoped resources (such as ClusterRole and ValidatingWebhookConfiguration) that they cannot create directly, achieving cross-tenant privilege escalation and cluster-level attacks. The attack vector has a few limiting factors. This attack requires Tenant Owner privileges and requires Capsule Controller running with cluster-admin privileges (default configuration). Additionally, some clusters may have additional admission controllers blocking malicious resources. Version 0.13.0 patches this issue.

GHSA-qjjm-7j9w-pw72 — Capsule TenantResource RawItems Cluster-Scoped Resource Creation Vulnerability

Affected: Go: github.com/projectcapsule/capsule

# TenantResource RawItems Cluster-Scoped Resource Creation Vulnerability

## Summary

The Capsule Controller runs with cluster-admin privileges. Although the TenantResource RawItems processing logic forcibly sets the namespace, this is ineffective for cluster-scoped resources. Tenant administrators can leverage the Controller's elevated privileges to create cluster-scoped resources (such as ClusterRole and ValidatingWebhookConfiguration) that they cannot create directly, achieving cross-tenant privilege escalation and cluster-level attacks.

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## Details

### Vulnerability Location

File: `internal/controllers/resources/processor.go` Function: `HandleSection()` Lines: 247-285

### Core Issues

1. **Excessive Controller Privileges**: The Controller's ServiceAccount is bound to the cluster-admin ClusterRole ```yaml # ClusterRoleBinding: capsule-manager-rolebinding roleRef: kind: ClusterRole name: cluster-admin ```

2. **Missing Resource Scope Validation**: Although the code calls `obj.SetNamespace(ns.Name)`, this is ineffective for cluster-scoped resources (ClusterRole, ValidatingWebhookConfiguration, etc.), as the Kubernetes API ignores this field

3. **Missing Resource Type Validation**: No check for whether resources are cluster-scoped

### Vulnerable Code Analysis

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

t := fasttemplate.New(template, "{{ ", " }}")…