Affected: Go: github.com/docker/docker

Moby is an open source container framework developed by Docker Inc. that is distributed as Docker Engine, Mirantis Container Runtime, and various other downstream projects/products. The Moby daemon component (dockerd), which is developed as [moby/moby](https://github.com/moby/moby) is commonly referred to as Docker, or Docker Engine.

Firewalld is a daemon used by some Linux distributions to provide a dynamically managed firewall. When Firewalld is running, Docker uses its iptables backend to create rules, including rules to isolate containers in one bridge network from containers in other bridge networks.

### Impact

The iptables rules created by Docker are removed when firewalld is reloaded using, for example "firewall-cmd --reload", "killall -HUP firewalld", or "systemctl reload firewalld".

When that happens, Docker must re-create the rules. However, in affected versions of Docker, the iptables rules that isolate containers in different bridge networks from each other are not re-created.

Once these rules have been removed, containers have access to any port, on any container, in any non-internal bridge network, running on the Docker host.

Containers running in networks created with `--internal` or equivalent have no access to other networks. Containers that are only connected to these networks remain isolated after a firewalld reload.

Where Docker Engine is not running in the host's network namespace, it is unaffected. Including, for example, Rootless Mode, and Docke…