# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-UBU-SVC-023
title: Disable the CUPS print server and printer discovery
finding:
  title: The CUPS print service runs on a system that does not print
  description: CUPS and cups-browsed parse print jobs and printer announcements, and have had remotely exploitable flaws.
status: active
profiles: [server, desktop-hardened]
risk:
  severity: medium
assessment: automated
tags: [services, cups, printing, attack-surface]

description: |
  CUPS is started by `cups.service`, `cups.socket` and `cups.path`; `cups-browsed.service`
  discovers network printers and adds them automatically.

  The control passes when each unit is masked or not installed at all.
rationale: |
  The print stack parses complex documents and network announcements. Flaws in `cups-browsed`
  have allowed remote code execution by announcing a malicious printer. Servers rarely print.
impact: |
  The system can no longer print, and network printers are no longer discovered. Print servers
  and desktops that print keep CUPS: the control is only in the server and hardened desktop
  profiles, and can be excluded in the tailoring file.
notes: |
  The socket and path units can start `cupsd` on their own, so they are masked too.

audit:
  manual: |
    Run `systemctl is-enabled cups.service cups.socket cups.path cups-browsed.service`. Each must
    print `masked`, or fail because the unit does not exist.
  logic: all
  checks:
    - id: cups-browsed
      engine: systemd-unit
      description: Printer discovery daemon.
      spec: { unit: cups-browsed.service, state: masked }
    - id: cups-socket
      engine: systemd-unit
      description: CUPS socket activation.
      spec: { unit: cups.socket, state: masked }
    - id: cups-path
      engine: systemd-unit
      description: CUPS path activation.
      spec: { unit: cups.path, state: masked }
    - id: cups
      engine: systemd-unit
      description: CUPS scheduler.
      spec: { unit: cups.service, state: masked }

remediation:
  manual: |
    Run `systemctl mask --now cups-browsed.service cups.socket cups.path cups.service`, or
    `apt purge cups cups-daemon cups-browsed` if nothing depends on them.
  effects:
    restart: none
    disruption: low
    lockout_risk: false
  rollback: |
    Run `systemctl unmask cups-browsed.service cups.socket cups.path cups.service` then
    `systemctl enable --now cups.service cups-browsed.service`.
  scripts:
    - id: cups-browsed
      from_check: cups-browsed
    - id: cups-socket
      from_check: cups-socket
    - id: cups-path
      from_check: cups-path
    - id: cups
      from_check: cups

references:
  - title: cupsd(8), Ubuntu manual pages
    url: https://manpages.ubuntu.com/manpages/noble/man8/cupsd.8.html
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: cups-browsed(8), Ubuntu manual pages
    url: https://manpages.ubuntu.com/manpages/noble/man8/cups-browsed.8.html
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R62)
    url: https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
    publisher: ANSSI
    kind: guide
    accessed: 2026-10-19
mappings:
  - framework: anssi-linux
    framework_version: "2.0"
    id: R62
    relation: partial
    note: R62 asks to disable every unneeded service and names CUPS; this control covers it.
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-7
    relation: partial
  - framework: cis-ubuntu-2004
    framework_version: "3.0.0"
    id: "2.1.11"
    relation: equivalent
  - framework: cis-ubuntu-2204
    framework_version: "3.0.0"
    id: "2.1.11"
    relation: equivalent
  - framework: cis-ubuntu-2404
    framework_version: "2.0.0"
    id: "2.1.14"
    relation: equivalent
  - framework: cis-ubuntu-2604
    framework_version: "1.0.0"
    id: "2.1.11"
    relation: equivalent
threats:
  - framework: mitre-attack
    id: T1210
  - framework: cwe
    id: CWE-20

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["20.04"]
    environment: Proxmox VM, Ubuntu 20.04 cloud image, kernel 5.4.0-216-generic
    notes: "Stock image passes (units absent); with cups installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["22.04"]
    environment: Proxmox VM, Ubuntu 22.04 cloud image, kernel 5.15.0-198-generic
    notes: "Stock image passes (units absent); with cups installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["24.04"]
    environment: Proxmox VM, Ubuntu 24.04 cloud image, kernel 6.8.0-147-generic
    notes: "Stock image passes (units absent); with cups installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["26.04"]
    environment: Proxmox VM, Ubuntu 26.04 cloud image, kernel 7.0.0-38-generic
    notes: "Stock image passes (units absent); with cups installed the check fails, server-hardened remediation masks the units, audit passes, unchanged on a second run and after reboot."
introduced_in: 0.1.0
created: 2026-10-19
updated: 2026-10-19