Executive brief
Capsule, a multi-tenancy tool for Kubernetes, contains a vulnerability that allows a tenant owner to bypass security restrictions and create cluster-wide resources. By exploiting this flaw, an attacker with limited access to a single tenant can escalate their privileges to become a cluster administrator. This could lead to a total compromise of the entire Kubernetes cluster, including access to sensitive data and control over all other tenants.
Technical details
A vulnerability exists in Capsule where the fix for CVE-2026-22872 was incomplete. While a cluster-scope rejection guard was added to the NamespacedItems selection path, it was omitted from the RawItems and Generators creation paths in the TenantResource controller. An attacker with Tenant Owner privileges can submit a TenantResource containing cluster-scoped objects (like ClusterRoles or ValidatingWebhookConfigurations) in the 'rawItems' or 'generators' fields. Because the controller applies these resources using its own high-privilege ServiceAccount and the Kubernetes API ignores namespace settings for cluster-scoped objects, the attacker achieves cluster-admin equivalent privileges. This issue is patched in version 0.13.8.
Affected products
- Project Capsule Capsule >= 0.13.0, <= 0.13.7
Timeline
- 2026-07-08: disclosed: Advisory published by project maintainers
- 2026-07-08: patched: Fixed in version 0.13.8
- 2026-07-30: advisory: NVD published CVE-2026-65835