NIST SP 800-53 Rev. 5 SR-3(3) — Sub-Tier Flow Down

What this control requires

Ensure that supply chain risk management controls included in prime contractor contracts are also extended to subcontractors. This ensures comprehensive risk management across all levels of the supply chain. This control supports the Procurement, Vendor Management, Compliance capability within the Supply Chain Risk Management family.

In plain English

Ensure that supply chain risk management controls included in prime contractor contracts are also extended to subcontractors. In practice, this means you can prove you security management-level controls on a defined cadence.

Why it matters

SP 800-53 is the catalogue every U.S. federal authorisation (FedRAMP, FISMA, CMMC) and most regulated industries point at. A missing control surfaces as a Plan of Action & Milestones (POA&M) item that an Authorizing Official must approve before the Authority To Operate is granted or renewed.

This control is rated high. Auditors expect a named owner, a remediation SLA, and a tooling artefact that evidences continuous operation.

What an auditor looks for

A 3PAO (FedRAMP) or Independent Assessor (NIST RMF) tests against NIST SP 800-53A assessment procedures. For each control they expect a documented implementation that addresses every assessment objective (Examine, Interview, Test) and an implementation summary in the System Security Plan.

Within Supply Chain Risk Management, the assessor will trace your implementation back to the catalogue reference (Control SR-3(3)) and look for objective evidence on the latest two assessment cycles.

How to implement

1. Write a short policy stating intent, scope and named owner.
2. Encode it as a platform guardrail — SCP, Azure Policy initiative, Organisation Policy, or repository policy.
3. Wire a monitoring signal that catches drift (CSPM rule, SIEM rule, scheduled query, Workspace alert) and ticket it.
4. Review on a documented cadence and capture the review in the risk register or compliance tracker.

Operational checklist

• Security. Document the trigger, the owner and the cadence.
• Chain. Document the trigger, the owner and the cadence.
• Control. Document the trigger, the owner and the cadence.
• Compliance. Document the trigger, the owner and the cadence.
• Supply. Document the trigger, the owner and the cadence.
• Scope: management, controls, compliance, capability, security, levels, procurement, flow down.

Evidence to collect

• Vendor Risk Management. vendor_risk_management evidence

Third-party risk management evidence (assessments, contracts, due diligence) shows supplier oversight. Focus: Sub-Tier Flow Down.

How it maps to other frameworks

Computed from shared tags, control component and key-operation subjects — handy when you are reconciling controls across an audit.

• ISO/IEC 27001:2022 A.5.19 — Information security in supplier relationships
• NIST SP 800-171 Rev. 3 3.16.2 — Unsupported System Components
• SOC 2 (2017 TSC) CC9.2 — Vendor Risk Management
• BSI C5:2020 OIS-03 — Interfaces and Dependencies
• ISO/IEC 42001:2023 A.10.2 — Allocation of responsibilities

Related controls in NIST SP 800-53 Rev. 5

• Control SR-3(2) — Limitation Of Harm
• Control SR-5(1) — Adequate Supply
• Control SR-3(1) — Diverse Supply Base
• Control SR-3 — Supply Chain Controls And Processes
• Control SR-6 — Supplier Assessments And Reviews
• Control SA-12(2) — Supplier Reviews

References

• NIST Computer Security Resource Center — NIST SP 800-53 Rev. 5
• Catalogue identifier: Control SR-3(3)

Topics: governance riskvendor riskvendor managementsupply chain securitythird party monitoring