Contour · Contour · CVE-2021-32783
**Name of the Vulnerable Software and Affected Versions**
Contour versions prior to 1.17.1
Contour versions prior to 1.18.0
**Description**
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, or to expose the existence of any Secret that Envoy is using for its configuration, including most notably TLS Keypairs. However, it cannot be used to get the content of those secrets. Since this attack allows access to the administration interface, a variety of administration options are available, such as shutting down the Envoy or draining traffic. In general, the Envoy admin interface cannot easily be used for making changes to the cluster, in-flight requests, or backend services, but it could be used to shut down or drain Envoy, change traffic routing, or to retrieve secret metadata.
**Recommendations**
For versions prior to 1.17.1, update to version 1.17.1 or later to address the issue.
For versions prior to 1.18.0, update to version 1.18.0 or later to address the issue.
As a temporary workaround, consider disabling ExternalName type Services by default, or block obvious "localhost" entries when ExternalName Services are enabled.
Restrict access to the administration interface to minimize the risk of exploitation.