# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-UBU-BOOT-001
title: Enable full address space layout randomization
finding:
  title: Memory layout of processes is predictable
  description: Without full randomization, an attacker exploiting a memory bug can guess where code and data live.
status: active
profiles: [core]
risk:
  severity: medium
assessment: automated
tags: [kernel, sysctl, memory]

description: |
  The `kernel.randomize_va_space` sysctl controls address space layout randomization (ASLR).
  With the value `2`, the kernel randomizes the positions of the stack, the virtual dynamic
  shared object page, shared memory regions and the data segment (heap) of every process.
rationale: |
  Most memory corruption exploits need to know the address of the code or data they target.
  Randomizing the layout at every execution turns a reliable exploit into a guess, and makes
  return-oriented programming much harder.
impact: |
  None known. `2` is the kernel default and the Ubuntu default.
notes: |
  `1` randomizes everything except the heap, `0` disables ASLR. A program that needs ASLR off
  for debugging can be started with `setarch -R` instead of changing the system setting.

setting:
  location: sysctl `kernel.randomize_va_space`, persisted in `/etc/sysctl.d/`
  default_value: "2"
  recommended_value: "2"

audit:
  manual: |
    Run `sysctl kernel.randomize_va_space`. The value must be `2`.
    Then check that no file in `/etc/sysctl.conf`, `/etc/sysctl.d/`, `/run/sysctl.d/`
    or `/usr/lib/sysctl.d/` sets it to another value.
  checks:
    - id: running
      engine: sysctl
      description: Running value of kernel.randomize_va_space.
      spec: { key: kernel.randomize_va_space, value: 2 }

remediation:
  manual: |
    Create `/etc/sysctl.d/60-cirsec.conf` containing `kernel.randomize_va_space = 2`,
    remove any other assignment of this key, then run `sysctl --system`.
  effects:
    restart: none
    disruption: none
    lockout_risk: false
  rollback: |
    Remove the line from `/etc/sysctl.d/60-cirsec.conf` and run `sysctl --system`.
  scripts:
    - id: set
      from_check: running

references:
  - title: Ubuntu Security documentation - Address space layout randomization
    url: https://documentation.ubuntu.com/security/security-features/process-memory/aslr/
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: Linux kernel documentation - Documentation for /proc/sys/kernel/ (randomize_va_space)
    url: https://docs.kernel.org/admin-guide/sysctl/kernel.html
    publisher: The Linux Kernel Organization
    kind: vendor-doc
    accessed: 2026-10-19
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R9)
    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: R9
    relation: partial
    note: R9 lists several kernel settings; this control covers kernel.randomize_va_space.
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: SC-30
    relation: related
  - framework: cis-ubuntu-2004
    framework_version: "3.0.0"
    id: "1.5.1"
    relation: equivalent
  - framework: cis-ubuntu-2204
    framework_version: "3.0.0"
    id: "1.5.1"
    relation: equivalent
  - framework: cis-ubuntu-2404
    framework_version: "2.0.0"
    id: "1.5.9"
    relation: equivalent
  - framework: cis-ubuntu-2604
    framework_version: "1.0.0"
    id: "1.5.9"
    relation: equivalent
threats:
  - framework: mitre-attack
    id: T1068
  - framework: cwe
    id: CWE-119

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, BIOS boot
    notes: "Passes on a fresh install; audit, remediate, audit for core and server-hardened; still passes 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, BIOS boot
    notes: "Passes on a fresh install; audit, remediate, audit for core and server-hardened; still passes 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, BIOS boot
    notes: "Passes on a fresh install; audit, remediate, audit for core and server-hardened; still passes 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, BIOS boot
    notes: "Passes on a fresh install; audit, remediate, audit for core and server-hardened; still passes after reboot."
introduced_in: 0.1.0
created: 2026-10-19
updated: 2026-10-19