Lab: Host mounts and privileged containers

DISCLAIMER: Host bind mounts of / and --privileged containers are unsafe. Run this lab only on an isolated Linux VM you own. Do not use production or shared systems.

See how bind mounts erase practical separation between a container and the host. The goal is to recognize flags your policies should block.

Lab objective

Lab Objective

• Demonstrate host filesystem exposure via bind mounts.
• Show host-level access using --privileged + nsenter.
• Prove real impact: read, modify, and persist on host from container.
• Map each action to what a policy should block.

Host Filesystem Exposure via Bind Mount

• Run container with full host mount.

docker run -it --rm --privileged -v /:/host ubuntu bash

• Mounts entire host filesystem inside container

• Read host sensitive files.

ls -la /host/etc/passwd
cat /host/etc/hostname

• Confirms visibility into host system files

Impact: Modify and Persist on Host

• Create file on host from inside container.

echo "owned-by-container" > /host/tmp/pwned.txt

• Writes directly to host filesystem

• Exit container and verify from host.

cat /tmp/pwned.txt

• Confirms file write and persistence on host

• Next step: Theory: Image CVE scanners, then Lab: Trivy image scan.