Ensure that Docker's default bridge "docker0" is not used

LowLevel 2Automateddocker

Description

Containers on the default bridge (docker0) can reach each other without restriction and are exposed to ARP spoofing; user-defined networks should be used. Flags containers attached to the network named bridge. The audit inspects every running container (docker ps -q) and prints the offending names; a host with no running containers is compliant.

How it is checked

Audit method: Shell command

shell

ids=$(docker ps -q) || exit 1; [ -z "$ids" ] && { echo compliant; exit 0; }; out=$(docker inspect --format '{{.Name}}{{range $n, $_ := .NetworkSettings.Networks}} {{$n}}{{end}}' $ids) || exit 1; bad=$(printf '%s\n' "$out" | awk '{for(i=2;i<=NF;i++) if($i=="bridge") {print $1; break}}'); [ -z "$bad" ] && echo compliant || printf '%s\n' "$bad"

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Create user-defined networks (docker network create ...) and attach containers to them instead of the default bridge.

Properties

Operating systems: Any
Tags: dockerruntimenetwork
Reference: CIS Docker Benchmark v1.9.0 - 5.30 Ensure that Docker's default bridge "docker0" is not used

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target docker --level 2