# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-DEB-SVC-027
title: Remove the NFS client utilities when no NFS share is mounted
finding:
  title: NFS client utilities are installed on a system that mounts no NFS share
  description: The NFS client stack adds setuid helpers and RPC daemons that are not needed.
status: active
profiles: [server-hardened]
risk:
  severity: low
assessment: automated
tags: [packages, nfs, attack-surface]

description: |
  `nfs-common` provides the NFS client tools: the `mount.nfs` setuid helper, `rpc.statd` (NFSv3
  locking), `rpc.gssd` and `rpc.idmapd`. It is only needed to mount NFS shares.
rationale: |
  Unneeded software is extra code to patch. `mount.nfs` runs with root privileges, and
  `rpc.statd` listens for RPC requests when it is started.
impact: |
  NFS shares can no longer be mounted. Removing `nfs-common` also removes `nfs-kernel-server` if it
  is installed. Systems that mount NFS shares must exclude this control in their tailoring file.
notes: |
  Not installed on Debian cloud images; often pulled in by full server installs. The NFS server
  and rpcbind are handled by CB-DEB-SVC-003.

audit:
  manual: |
    Run `dpkg-query -W -f='${Status}\n' nfs-common`. It must not print `install ok installed`.
  checks:
    - id: nfs-common
      engine: package
      description: NFS client utilities.
      spec: { name: nfs-common, state: absent }

remediation:
  manual: |
    Check that `findmnt -t nfs,nfs4` lists nothing and that no NFS entry remains in `/etc/fstab`,
    then run `apt purge nfs-common`.
  effects:
    restart: none
    disruption: low
    lockout_risk: false
  rollback: |
    Run `apt install nfs-common`.
  scripts:
    - id: nfs-common
      from_check: nfs-common

references:
  - title: nfs(5), Debian manual pages
    url: https://manpages.debian.org/trixie/nfs-common/nfs.5.en.html
    publisher: Debian
    kind: vendor-doc
    accessed: 2026-10-18
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R58)
    url: https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
    publisher: ANSSI
    kind: guide
    accessed: 2026-10-18
mappings:
  - framework: anssi-linux
    framework_version: "2.0"
    id: R58
    relation: partial
    note: R58 asks to install only the packages that are strictly needed; this control covers nfs-common.
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-7
    relation: partial
threats:
  - framework: mitre-attack
    id: T1210
related_controls:
  - id: CB-DEB-SVC-003
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["12"]
    environment: Proxmox VM, Debian 12 genericcloud image, kernel 6.1.0-54-cloud-amd64
    notes: "Fresh image passes; with nfs-common installed the check fails, fix purges it (after CB-DEB-SVC-003 removed the NFS server), audit passes after reboot."
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["13"]
    environment: Proxmox VM, Debian 13 genericcloud image, kernel 6.12.113+deb13-cloud-amd64
    notes: "Fresh image passes; with nfs-common installed the check fails, fix purges it (after CB-DEB-SVC-003 removed the NFS server), audit passes after reboot."
introduced_in: 0.1.0
created: 2026-10-18
updated: 2026-10-18