---
title: "NIST 800-171 3.1.3 (AC.L2-3.1.3): CUI Flow Control"
description: "NIST SP 800-171 3.1.3 CUI Flow Control: 1 SPRS point, allowed on a CMMC POA&M. The text, what assessors check and the evidence."
url: https://policycortex.com/nist-800-171/access-control/3.1.3
sealed: 2026-11-11
amended: 2026-11-11
register: nist-800-171/access-control/3.1.3
records: 7
digest: sha3:a97505d3d423ca9b3cf5bc85f62f3e491056b75053c9f2155ce1022df8be3cd7
---

# NIST 800-171 3.1.3 (AC.L2-3.1.3): CUI Flow Control

NIST 800-171 / Access Control / 3.1.3

"Control the flow of CUI in accordance with approved authorizations." ([NIST SP 800-171 Rev. 2, requirement 3.1.3](https://doi.org/10.6028/NIST.SP.800-171r2))

CMMC Level 2 practice AC.L2-3.1.3.

## What 3.1.3 means in practice

This requirement is about where CUI may travel, not who may read it. Decide which networks, systems, people and services CUI may move between, then enforce those routes with firewalls, network rules, proxies or data loss prevention, so CUI cannot leave the approved paths by accident.

## SPRS points and the CMMC POA&M

- **CMMC Level 2 practice**: AC.L2-3.1.3
- **SPRS points**: 1 point. When it is not met, the DoD Assessment Methodology subtracts 1 from the score of 110.
- **CMMC POA&M**: Allowed. It is worth 1 point, and 32 CFR 170.21(a)(2)(ii) admits requirements worth 1 point. Conditional status also needs a score of at least 88, and the item must be closed within 180 days.

Sources: [NIST SP 800-171 DoD Assessment Methodology, version 1.2.1 (June 24, 2020), Annex A](https://www.acq.osd.mil/asda/dpc/cp/cyber/docs/safeguarding/NIST-SP-800-171-Assessment-Methodology-Version-1.2.1-6.24.2020.pdf); [32 CFR 170.21, Plan of Action and Milestones requirements](https://www.ecfr.gov/current/title-32/section-170.21).

## What an assessor checks for 3.1.3

NIST SP 800-171A gives 5 determination statements for 3.1.3, each found satisfied or other than satisfied. Determine if:

- 3.1.3[a] information flow control policies are defined.
- 3.1.3[b] methods and enforcement mechanisms for controlling the flow of CUI are defined.
- 3.1.3[c] designated sources and destinations (e.g., networks, individuals, and devices) for CUI within the system and between interconnected systems are identified.
- 3.1.3[d] authorizations for controlling the flow of CUI are defined.
- 3.1.3[e] approved authorizations for controlling the flow of CUI are enforced.

[NIST SP 800-171A (June 2018), assessment objectives for 3.1.3](https://doi.org/10.6028/NIST.SP.800-171A)

## Evidence that shows 3.1.3 is met

- A data flow diagram showing where CUI enters, moves within and leaves the system boundary.
- The written information flow policy naming approved sources and destinations for CUI.
- Firewall, network security group or proxy rules that enforce those routes.
- Data loss prevention or mail gateway rules that stop CUI from reaching unapproved destinations.

## How PolicyCortex gathers the evidence

PolicyCortex reads this evidence with the collectors below, read only, and grades 3.1.3 from it. Each line says what the product checks.

- **Azure: Network security groups.** Checks that network security group rules control the network traffic that can flow between enclaves.
- **AWS: EC2 and VPC networking.** Checks that security groups restrict SSH and common ports from the internet and that each VPC's default security group has no rules.
- **AWS: S3 buckets.** Checks that no S3 bucket is publicly readable or publicly writable.

## Related pages

- **Calculator**: [SPRS score calculator: mark 3.1.3 and the other 109 requirements and see the score.](https://policycortex.com/sprs-score-calculator#family-AC)
- **Sample package**: [Sample package: an SSP, a POA&M and an evidence chain the product generated from demonstration data.](https://policycortex.com/sample-package)
- **Family**: [All 22 Access Control requirements (3.1).](https://policycortex.com/nist-800-171/access-control)
- **Previous**: [3.1.2: Transaction Control](https://policycortex.com/nist-800-171/access-control/3.1.2)
- **Next**: [3.1.4: Separation of Duties](https://policycortex.com/nist-800-171/access-control/3.1.4)
- **All requirements**: [All 110 NIST SP 800-171 requirements, by family.](https://policycortex.com/nist-800-171)

Meet the requirement once. Keep the evidence current. [Request Access](https://app.policycortex.com/auth?mode=request-access) · [Book a call](https://policycortex.com/book)

## Register colophon

| Seq | Label | SHA3-256 | Prev |
|---|---|---|---|
| REC 0000 | REQUIREMENT | 649b00c77994 | ca7a33e9388b |
| REC 0001 | MEANING | 1d37b9660b5d | 649b00c77994 |
| REC 0002 | POINTS AND POA&M | 0e67e94a5744 | 1d37b9660b5d |
| REC 0003 | ASSESSMENT OBJECTIVES | 368ad5ac494e | 0e67e94a5744 |
| REC 0004 | EVIDENCE | d37189f3abdb | 368ad5ac494e |
| REC 0005 | COLLECTORS | 3f5162d6e2e4 | d37189f3abdb |
| REC 0006 | RELATED | a97505d3d423 | 3f5162d6e2e4 |

Head sha3:a97505d3d423ca9b3cf5bc85f62f3e491056b75053c9f2155ce1022df8be3cd7. Each digest is SHA3-256 over the previous digest, the register key, the record label, and the record copy; a second party can recompute it from this document.