---

name: "docker-security-review" description: "Review a Dockerfile or Compose file for root runtime, latest tags, secrets in layers, and the Docker socket. Use for a Docker security review. Do not use for a non-container change or to mount the Docker socket into an app container."

Docker Security Review Skill for Copilot

Copilot skill docker-security-review for Docker. The description decides when Copilot loads it. Keep this copy under .github/skills.

When to run

Run this review for a Dockerfile, a Compose file, or a request to "check the image".

When to leave it

Do not upgrade dependencies or the framework version unless the user asked.

Stop for a change that does not touch containers. Do not push an image or log into a registry.

Steps

1. Read the base image reference. latest, or no pin at all, is a high finding.
2. Search for ARG and ENV values that look like tokens, and for COPY of .env. A secret in a layer is a high finding. Recommend a BuildKit secret mount.
3. Confirm the runtime stage sets USER to a non-root user. Root is a high finding unless the comment explains a hard requirement.
4. Search Compose for privileged, docker.sock, and published database ports. Each is a high finding in an app service.
5. Confirm a healthcheck and that the process can receive SIGTERM.
6. Build only if the user asked and the daemon is local. Otherwise write not run. Do not push.

Output

Findings with severity, file, line, the insecure instruction, and the replacement. No registry credentials in the report.

## Findings
- high | path:line | what is wrong | what to do instead

## No findings
Say "No findings" and list the files you opened. A search you skipped is not a clean result.

## Example
Input: a runtime stage ends with `USER root` and `ENV DATABASE_URL=postgres://app:secret@db/app`.
Output: high | Dockerfile:18 | the process runs as root and the database URL is baked into the image | `USER node`. Pass `DATABASE_URL` when the container starts, from Compose, Kubernetes, or the runtime environment. A BuildKit secret mount exists only during the build. Use it for a build-time credential, not for this URL.

Do not flag the valid pattern named in the standards. Flag the mistake next to it.

What to check

• Image: a latest base tag, or a runtime stage that copies a secret file into the image.
• Secrets: a token in ARG, ENV, or a committed .env in the build context.
• User: the runtime stage leaves the process as root.
• Socket: the Docker socket is mounted into a container.
• Privileges: --privileged or a broad capability with no written reason.

Stop

Stop when the user asks you to mount the Docker socket or to commit a .env into the build context.

Severity

high is a bug a caller can hit or a secret that leaks. medium is a broken contract that needs a specific input. low is a cleanup that does not change behaviour.