# Cis Docker 5.30

> Cis Docker 5.30 is an Agent Skill for devops & security published in the CyberStrikeus/CyberStrike repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Ensure that Docker's default bridge docker0 is not used

- Skill name: `cis-docker-5.30`
- Category: [DevOps & Security](https://www.openparable.com/skill/devops-security/1)
- Source: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Server_Software/Docker/CIS_Docker_Benchmark_v1.8.0/cis-docker-5.30/SKILL.md
- Repository: CyberStrikeus/CyberStrike (1,211 GitHub stars when collected)

## SKILL.md

# 5.30 Ensure that Docker's default bridge "docker0" is not used (Manual)

## Profile Applicability

- Level 2 - Docker - Linux

## Description

You should not use Docker's default bridge `docker0`. Instead you should use Docker's user-defined networks for container networking.

## Rationale

Docker connects virtual interfaces created in bridge mode to a common bridge called `docker0`. This default networking model is vulnerable to ARP spoofing and MAC flooding attacks as there is no filtering applied to it.

## Impact

User-defined networks need to be configured and managed in line with organizational security policy.

## Audit Procedure

You should run the command below, and verify that containers are on a user-defined network and not the default `docker0` bridge.

```
docker network ls --quiet | xargs docker network inspect --format '{{ .Name }}: {{ .Options }}'
```

## Remediation

You should follow the Docker documentation and set up a user-defined network. All the containers should be run in this network.

## Default Value

By default, Docker runs containers within the default `docker0` bridge.

## References

1. https://docs.docker.com/network/bridge/

## CIS Controls

| Controls Version | Control                                                                                                                                                                                                                                              | IG 1 | IG 2 | IG 3 |
| ---------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---- | ---- | ---- |
| v8               | 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software<br>Uninstall or disable unnecessary services on enterprise assets and software, such as an unused file sharing service, web application module, or service function. |      | ●    | ●    |
| v6               | 9 Limitation and Control of Network Ports, Protocols, and Services<br>Limitation and Control of Network Ports, Protocols, and Services                                                                                                               |      |      |      |

---

Source: https://www.openparable.com/skill/devops-security/cis-docker-5-30 (OpenParable). Cite the canonical URL above.