NIST SP 800-171 vs. CMMC: What’s the Difference?

NIST SP 800-171 and the Cybersecurity Maturity Model Certification (CMMC) both exist to protect Controlled Unclassified Information (CUI), but they are not interchangeable. The key difference is simple: CMMC adds enforcement.

High-Level Overview

NIST SP 800-171 defines 110 security requirements for protecting CUI in non-federal systems. Contractors implement and self-assess these controls, then report scores in SPRS under DFARS requirements.

CMMC builds on NIST SP 800-171 by adding a certification layer. For many contracts, compliance must be validated before award, not attested after the fact.

Key Differences That Matter

• Assessment model
  NIST SP 800-171 relies on self-assessment.
  CMMC may require a third-party assessment by a C3PAO for Level 2 contracts.

• Enforcement mechanism
  NIST SP 800-171 is enforced through DFARS clauses and reporting.
  CMMC is enforced at contract award. If you are not certified, you cannot bid.

• Risk tolerance
  Under 800-171, gaps may persist if documented.
  Under CMMC, gaps often mean ineligibility.

How Contractors Should Prepare

Organizations should continue performing NIST SP 800-171 self-assessments, but preparation cannot stop there. CMMC requires stronger evidence, tighter scoping, and assessor validation.

Align your controls, documentation, and System Security Plan now so the transition from self-attestation to certification does not delay eligibility.

Why This Matters

Many contractors assume that meeting NIST SP 800-171 automatically means they are CMMC-ready. That assumption is costly. Alignment helps, but certification is the gate.

NIST SP 800-171 defines the controls. CMMC decides whether you can compete.