GHSA-6fwg-jrfw-ff7p

Traefik docker container using 100% CPU

### Summary The traefik docker container uses 100% CPU when it serves as its own backend, which is an automatically generated route resulting from the Docker integration in the default configuration. ### Details While attempting to set up Traefik to handle traffic for Docker containers, I observed in the webUI a rule with the following information: `Host(traefik-service) | webwebsecure | traefik-service@docker | traefik-service` I assumed that this is something internal; however, I wondered why it would have a host rule on the web entrypoint configured. So I have send a request with that hostname with `curl -v --resolve "traefik-service:80:xxx.xxx.xxx.xxx" http://traefik-service`. That made my whole server unresponsive. I assume the name comes from a docker container with that name, traefik itself: ``` localhost ~ # docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES d1414e74aec7 traefik:v2.10 "/entrypoint.sh trae…" 4 minutes ago Up 4 minutes 0.0.0.0:80->80/tcp, :::80->80/tcp, 0.0.0.0:443->443/tcp, :::443->443/tcp, 127.0.0.1:8080->8080/tcp traefik.service ``` ### PoC 1. Start traefik with `docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -p 80:80 --name foo -p 8080:8080 traefik:v2.10 --api.insecure=true --providers.docker` 2. `curl -v --resolve "foo:80:127.0.0.1" http://foo` looks like this creates an endless loop of request. Knowing the name of the docker container seems to be enough to trigger this, if the docker backend is used. ### Impact Server is unreachable and uses 100% CPU