capsule-proxy service discloses Namespaces of colliding tenants to owners of different tenants with the same ServiceAccount name

Overview

Summary

A bug in the RoleBinding reflector used by capsule-proxy gives ServiceAccount tenant owners the right to list Namespaces of other tenants backed by the same owner kind and name.

Details

• Tenant solar, owned by a ServiceAccount named tenant-owner in the Namespace solar
• Tenant wind, owned by a ServiceAccount named tenant-owner in the Namespace wind

Please, notice the same ServiceAccount name, although in different namespaces.

The Tenant owner solar would be able to list the namespaces of the Tenant wind and vice-versa, although this is not correct.

The bug introduces an exfiltration vulnerability since allows the listing of Namespace resources of other Tenants, although just in some specific conditions:

1. capsule-proxy runs with the --disable-caching=false (default value: false)
2. Tenant owners are ServiceAccount, with the same resource name, but in different Namespaces.

The CVE doesn't allow any privilege escalation on the outer tenant Namespace-scoped resources, since the Kubernetes RBAC is enforcing this.

Affected packages

• github.com/projectcapsule/capsule < 0.4.5
• github.com/projectcapsule/capsule-proxy < 0.4.5

Remediation

Upgrade to a patched release:

• github.com/projectcapsule/capsule 0.4.5
• github.com/projectcapsule/capsule-proxy 0.4.5