# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-DEB-DESK-004
title: Never run software automatically from inserted media in GNOME
finding:
  title: GNOME can start programs from inserted media
  description: When a disc or USB device is inserted, GNOME may offer or start the program the medium declares, which a crafted medium can abuse.
status: active
profiles: [desktop]
risk:
  severity: medium
assessment: automated
tags: [gnome, dconf, removable-media]

applicability:
  facts: [desktop-gnome]

description: |
  `org.gnome.desktop.media-handling autorun-never` set to `true` stops GNOME from prompting
  for or launching programs when media are inserted. The key is set in the system dconf
  database `local` and locked.
rationale: |
  Autorun turns the insertion of a medium into code execution with one click, or none if the
  user chose "always". It is a classic infection path for removable media.
impact: |
  Users open media content themselves from the file manager.
notes: |
  Debian 13 already defaults to `true`; Debian 12 defaults to `false`. In both, users can
  change it unless the key is locked.

setting:
  location: /etc/dconf/db/local.d/, key /org/gnome/desktop/media-handling/autorun-never
  default_value: false (Debian 12), true (Debian 13), not locked
  recommended_value: true, locked

audit:
  manual: |
    1. `dconf read /org/gnome/desktop/media-handling/autorun-never` must print `true`.
    2. The key must be listed in a file of `/etc/dconf/db/local.d/locks/`.
  checks:
    - id: autorun-never
      engine: dconf
      description: GNOME never runs software from inserted media.
      facts: [desktop-gnome]
      spec:
        key: /org/gnome/desktop/media-handling/autorun-never
        value: "true"

remediation:
  manual: |
    1. Make sure `/etc/dconf/profile/user` contains `user-db:user` and `system-db:local`.
    2. Create `/etc/dconf/db/local.d/00-media-autorun`:
       ```
       [org/gnome/desktop/media-handling]
       autorun-never=true
       ```
    3. List `/org/gnome/desktop/media-handling/autorun-never` in
       `/etc/dconf/db/local.d/locks/00-media-autorun`.
    4. Run `dconf update`.
  effects:
    restart: session
    disruption: none
    lockout_risk: false
  rollback: |
    Delete the files written in `/etc/dconf/db/local.d/` and its `locks/` directory, then run
    `dconf update`.
  scripts:
    - id: autorun-never
      from_check: autorun-never

references:
  - title: gsettings-desktop-schemas - org.gnome.desktop.media-handling schema
    url: https://gitlab.gnome.org/GNOME/gsettings-desktop-schemas/-/blob/master/schemas/org.gnome.desktop.media-handling.gschema.xml.in
    publisher: The GNOME Project
    kind: vendor-doc
    accessed: 2026-10-18
  - title: GNOME System Administration Guide - Lock down specific settings
    url: https://help.gnome.org/admin/system-admin-guide/stable/dconf-lockdown.html.en
    publisher: The GNOME Project
    kind: vendor-doc
    accessed: 2026-10-18
mappings:
  - framework: cis-debian-12
    framework_version: "2.0.0"
    id: "1.7.5"
    relation: equivalent
  - framework: cis-debian-13
    framework_version: "1.1.0"
    id: "1.7.5"
    relation: equivalent
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-7
    relation: related
threats:
  - framework: mitre-attack
    id: T1091
related_controls:
  - id: CB-DEB-DESK-001
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["12"]
    environment: Proxmox VM with minimal GNOME (gdm3, gnome-shell), Debian 12 genericcloud image, kernel 6.1.0-54-cloud-amd64
    notes: "Generated dconf check and fix (desktop-hardened) on GNOME; value and lock confirmed with gsettings as a user; state kept after reboot."
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["13"]
    environment: Proxmox VM with minimal GNOME (gdm3, gnome-shell), Debian 13 genericcloud image, kernel 6.12.113+deb13-cloud-amd64
    notes: "Generated dconf check and fix (desktop-hardened) on GNOME; value and lock confirmed with gsettings as a user; state kept after reboot."
introduced_in: 0.1.0
created: 2026-10-18
updated: 2026-10-18