The most common and costly mistake is failing to identify all systems, people, and processes that touch CUI. Organizations often focus on their main servers and forget about email systems, backup solutions, personal devices, cloud storage, printers, and even physical document storage areas.

Fix: Conduct a thorough CUI data flow analysis before anything else. Map every point where CUI enters, moves through, is stored in, and exits your environment. Include digital AND physical flows.

We see too many SSPs filled with generic, copy-pasted language from templates. Assessors review SSPs daily — they can immediately tell when an organization hasn’t customized their plan. A vague SSP suggests vague implementation.

Fix: Every control description should name specific tools, specific configurations, specific personnel, and specific frequencies. “We use MFA” is not sufficient. “All users accessing the CUI enclave authenticate via Microsoft Authenticator push notifications as enforced by Azure AD Conditional Access Policy CA-001” is.

Your SSP says you review audit logs weekly. Can you prove it? Assessors will ask for evidence: screenshots, log exports, signed review forms, ticket numbers. If you can’t produce evidence, the control is considered “NOT MET” — regardless of what the SSP says.

Fix: Build an evidence library organized by control family. For every control in your SSP, maintain corresponding evidence: policy documents, configuration screenshots, log samples, training records, signed acknowledgments.

Organizations invest heavily in technical controls but overlook the Physical Protection (PE) family. Unlocked server rooms, unescorted visitors, CUI documents left on desks, and missing visitor logs are all findings that come up frequently.

Fix: Walk your facility with fresh eyes. Check access controls to server rooms and areas where CUI is processed. Implement a clean desk policy. Maintain visitor logs. Ensure media containing CUI (including paper) is properly marked, stored, and destroyed.

For CMMC Level 2, limited POA&Ms are permitted — but they must be properly documented with specific remediation steps, responsible parties, and realistic completion dates. Many contractors either have no POA&M at all or have entries so vague they’re useless.

Fix: Create a detailed POA&M for every control that is not fully implemented. Each entry needs: the specific gap, root cause, remediation plan, responsible individual (by name and title), required resources, milestones, and target completion date. Note that certain high-weighted controls cannot be on a POA&M at all.

MFA is required for all network access to the CUI environment. Common issues include: MFA not enforced for all users, SMS-based MFA being used (which is considered weak), MFA not covering all access points (VPN, email, cloud apps), and lack of MFA for privileged accounts accessing infrastructure.

Fix: Implement phishing-resistant MFA (FIDO2 keys, authenticator apps, or certificate-based) across all access points to the CUI environment. Ensure 100% of user accounts — including service accounts with interactive login — are covered.

Having an Incident Response Plan on paper is necessary but not sufficient. CMMC requires that the plan be tested. We frequently see organizations with an IR plan that’s never been exercised — no tabletop exercises, no simulations, no lessons-learned documentation.

Fix: Conduct at least one tabletop exercise per year simulating a realistic security incident. Document the exercise scenario, participants, findings, and improvements made as a result. Keep records of all exercises as evidence.

Security awareness training must be role-based and current. Common failures include: training content that hasn’t been updated in years, no record of who completed training, no specialized training for IT staff and system administrators, and no refresher training for new hires.

Fix: Implement annual security awareness training for all users and specialized training for IT staff. Track completion with a learning management system. Ensure content covers current threats, CUI handling procedures, and your organization’s specific policies.

Configuration Management is often underestimated. Common issues include: no baseline configurations documented, no change management process, unauthorized software installed on CUI systems, and default configurations still active on network devices.

Fix: Establish and document secure baseline configurations for all system types (workstations, servers, network devices, mobile). Implement a formal change management process. Maintain a current inventory of authorized software. Use automated tools (SCCM, Intune, GPOs) to enforce and monitor configurations.

Perhaps the most devastating mistake of all. Organizations wait until a contract requires CMMC certification, then realize they need 6-18 months of implementation work, plus scheduling time with a C3PAO that may have a 3-6 month backlog.

Fix: Start now. Even if you don’t have an immediate contract requiring CMMC, begin your gap assessment, build your SSP, and start implementing controls. The organizations that are already compliant when new contracts drop will have an enormous competitive advantage.

Prepare With Confidence

Our CMMC training course and toolkit are designed to help you avoid every mistake on this list.