GHSA-2v4p-qf9q-27wj: gRPC-Go xDS servers: Denial of Service (DoS) via crash due to missing `:authority` and `Host` headers

A vulnerability exists in gRPC-Go servers configured with `xds.NewGRPCServer()` where a crafted request missing both `:authority` and `Host` headers can cause a server panic, resulting in a Denial of Service (DoS). Servers built with `xds.NewGRPCServer` install an xDS routing interceptor on every RPC. This interceptor looks up the request’s `:authority` header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither `:authority` nor `Host`. …