CVE-2021-32783: Externally Controlled Reference to a Resource in Another Sphere

Contour is a Kubernetes ingress controller using Envoy proxy. In Contour a specially crafted ExternalName type Service may be used to access Envoy’s admin interface, which Contour normally prevents from access outside the Envoy container. This can be used to shut down Envoy remotely (a denial of service), or to expose the existence of any Secret that Envoy is using for its configuration, including most notably TLS Keypairs.