CVE-2020-15114: Missing Release of Resource after Effective Lifetime

In etcd before versions 3.3.23 and 3.4.10, the etcd gateway is a simple TCP proxy to allow for basic service discovery and access. However, it is possible to include the gateway address as an endpoint. This results in a denial of service, since the endpoint can become stuck in a loop of requesting itself until there are no more available file descriptors to accept connections on the gateway.