# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-M365-DEVICE-004
title: Limit the number of devices each user can join or register
finding:
  title: Users can join or register a large number of devices
  description: The per-user device quota is above the organization's limit, so a single account can add many device identities to the tenant.
status: active
profiles: [baseline]
risk:
  severity: low
assessment: manual
tags: [entra-id, device-registration, device-join, quota]

description: |
  The device setting **Maximum number of devices per user** is set to `{{ max_devices_per_user }}`
  or less. The quota counts Microsoft Entra joined and Microsoft Entra registered devices owned by
  each user. It does not apply to Microsoft Entra hybrid joined devices.
rationale: |
  Each device identity can hold a Primary Refresh Token and satisfy device-based Conditional
  Access conditions. A low quota limits how many device objects a compromised account can create,
  for persistence or to flood the directory, and keeps per-user inventories readable. Microsoft
  sets the default to 50, which is far above what a normal user needs.
impact: |
  Users who reach the limit cannot register or join another device until an old device is removed.
  Staff who handle many devices (technicians, test accounts) should use a device enrollment manager
  account or bulk provisioning instead of their own account. Combine with the cleanup of stale
  devices so that retired devices do not use up the quota.
notes: |
  Intune has a separate enrollment device limit (Devices > Device onboarding > Enrollment > Device
  limit restriction, 1 to 15). It does not replace this Entra quota, which applies even without
  Intune.

parameters:
  - name: max_devices_per_user
    type: integer
    description: Highest accepted value of the Entra per-user device quota.
    default: 10
    minimum: 1
    maximum: 100

setting:
  location: Microsoft Entra admin center > Entra ID > Devices > Device settings > Maximum number of devices per user
  default_value: "50"
  recommended_value: "{{ max_devices_per_user }} or less"

audit:
  manual: |
    1. Sign in to the Microsoft Entra admin center (https://entra.microsoft.com) as at least a
       Global Reader.
    2. Browse to **Entra ID** > **Devices** > **Device settings**.
    3. Read **Maximum number of devices per user**.
    4. Alternative, read only: `Invoke-MgGraphRequest -Method GET -Uri
       https://graph.microsoft.com/beta/policies/deviceRegistrationPolicy` and read
       `userDeviceQuota`.
    5. Fail if the value is greater than `{{ max_devices_per_user }}` or is **Unlimited**.

remediation:
  manual: |
    1. Find users above the target: in **Entra ID** > **Devices** > **All devices**, filter by
       owner, or export the list with **Download devices** and count devices per owner. Remove
       stale devices first.
    2. Browse to **Entra ID** > **Devices** > **Device settings**. Role: Cloud Device
       Administrator.
    3. Set **Maximum number of devices per user** to `{{ max_devices_per_user }}` (or lower) and
       save.
    4. Graph equivalent: `PUT https://graph.microsoft.com/beta/policies/deviceRegistrationPolicy`
       with the full policy object and `userDeviceQuota` set to the target value.
  rollback: |
    Raise **Maximum number of devices per user** back to the previous value.

references:
  - title: Manage devices in Microsoft Entra ID - Configure device settings
    url: https://learn.microsoft.com/entra/identity/devices/manage-device-identities
    publisher: Microsoft
    kind: vendor-doc
    accessed: 2026-10-24
mappings:
  - framework: cis-m365
    framework_version: "7.0.0"
    id: "5.1.4.2"
    relation: equivalent
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: AC-19
    relation: related
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-8
    relation: related
threats:
  - framework: mitre-attack
    id: T1098.005
related_controls:
  - id: CB-M365-DEVICE-003
    type: related
  - id: CB-M365-DEVICE-010
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
introduced_in: 0.1.0
created: 2026-10-24
updated: 2026-10-24