CVE-2026-22872 is a critical flaw (CVSS 9.1) in Capsule, the multi tenancy framework for Kubernetes. A tenant owner could use the controller's cluster admin rights to create cluster scoped objects such as ClusterRole and ValidatingWebhookConfiguration. Capsule 0.13.0 fixes the issue.
What's affected
Capsule versions before 0.13.0 are affected. The fixed version is 0.13.0.
The advisory states the limits clearly. The attacker needs Tenant Owner privileges. The controller must run with cluster admin privileges, which is the default configuration. Some clusters have additional admission controllers that may block the malicious resources.
How to check if you're exposed
Find the installed version and who holds tenant owner rights:
helm list -A | grep -i capsule
kubectl get deploy -A | grep -i capsule
kubectl get tenants
Read the image tag on the controller deployment and compare it to 0.13.0. Then list who can act as owner of each tenant. In a cluster where every tenant owner is a trusted platform team the exposure is small. Where tenants are separate customers or business units, treat this as urgent.
What to do now
- Upgrade Capsule to 0.13.0 or later using your normal Helm or manifest process.
- Review tenant owner assignments and remove any that are not needed.
- Check for unexpected ClusterRole, ClusterRoleBinding and webhook configuration objects created after tenant owners gained access.
- Keep admission policies that block cluster scoped resources from tenant driven paths as a second layer.
Why it matters
The record lists CWE-20 (Improper Input Validation) and CWE-863 (Incorrect Authorization). The controller forced a namespace on items it created, but that setting means nothing for objects that live at cluster scope, so the guard did not apply.
The result is a confused deputy. The tenant owner cannot create a ClusterRole directly, but the controller can, and it did so on request. Multi tenant systems need every privileged helper to check what the requester may do, not only where the object ends up. The record does not mark this CVE as exploited in the wild.
Try it yourself
Click through it at your own pace, or open it full screen.
Quick check
Do I need to be a tenant owner to abuse this?
Yes. The advisory says Tenant Owner privileges are required.
Does an admission controller fully protect me?
Not necessarily. The advisory says some clusters may block the resources, so upgrade rather than rely on that.
Sources
Last reviewed: 19 October 2026.
