Unauthorized Modification of Host Filesystem (`/home/linuxbrew` Created Without Permission)

[hopeseekr]

Summary:
Running the docker-wine launcher script modified my host system without consent. Specifically, it created the directory /home/linuxbrew on the host filesystem — even though my user does not have write access to /home and I did not grant the script permission to modify anything outside Docker.

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Steps to Reproduce

1. Download and execute the docker-wine launcher script (from this repository) as a normal user, e.g.:

   ./docker-wine

2. Observe that /home/linuxbrew is created on the host system.

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Expected Behavior

• The script should only start Docker containers and never modify the host environment.
• It should not install Homebrew, PulseAudio, XQuartz, or any other host-level packages.
• It should not create directories outside $HOME, particularly ones requiring elevated privileges like /home/linuxbrew.

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Actual Behavior

• After running the script, a new directory /home/linuxbrew was created on the host:

  ls -ld /home/linuxbrew
  drwxr-xr-x  5 root root ...

• My user cannot normally create this directory:

  mkdir /home/linuxbrew
  mkdir: cannot create directory ‘/home/linuxbrew’: Permission denied

• This indicates that a Docker container running as root wrote to the host filesystem via a bind mount.

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Security Impact

This behavior constitutes a security vulnerability:

• Containerized code executed as root modified the host filesystem outside of expected paths.
• No user consent or warning was provided.
• Host directories should never be altered unless explicitly specified via -v or similar options.

This could be exploited by a malicious Docker image or package install script to write arbitrary files on the host system as root.

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Environment

• Host OS: Linux (non-root user, /home not writable by normal users)
• Docker Version: 28.5.0
• docker-wine Version / Tag: latest
• Command Used: ./docker-wine
• Result: /home/linuxbrew created by container root

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Suggested Fix

1. Remove all automatic installation or host modification logic (install_xquartz, install_pulseaudio, etc.).

2. Never mount /home from the host into the container unless explicitly requested by the user.

3. Run containers with:

   --user $(id -u):$(id -g) --read-only --security-opt no-new-privileges

4. Add a prominent warning in the README about potential host modifications until resolved.

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Impact Severity:

High — Unauthorized host modification and potential privilege escalation through Docker bind mounts.