Broad VPN access often breaks the assessment story because it proves authentication, not least privilege. Users may gain network visibility far beyond what CMMC expects for CUI handling, which makes segmentation, monitoring, and audit evidence harder to defend. The control failure is not connectivity itself, but the absence of resource-level enforcement and demonstrable boundaries.
Why This Matters for Security Teams
Broad VPN access creates a misleading sense of readiness because it proves a user can enter the network, not that the user can only reach the CUI environment. For CMMC, that distinction matters. Assessors look for enforceable boundaries, least privilege, and evidence that access is limited to what the role actually requires. A flat or loosely segmented VPN can make those controls difficult to demonstrate, even when authentication is strong.
This is especially risky when identity controls are already weak. NHI Management Group has found that 97% of NHIs carry excessive privileges, which is why perimeter access alone does not solve the real problem. The operational lesson aligns with guidance in the OWASP Non-Human Identity Top 10 and NIST control expectations in NIST SP 800-53 Rev 5 Security and Privacy Controls: access must be constrained to the asset and action, not just the tunnel.
In practice, many security teams discover the problem only after a CMMC scoping discussion exposes that the VPN gives users more network reach than the evidence can defend.
How It Works in Practice
The assessment challenge is not that VPNs are inherently disallowed. The challenge is that a broad VPN often acts as a network-level pass, while CMMC readiness depends on showing that CUI is isolated by design. That means assessors expect segmentation, role separation, monitoring, and resource-level restrictions that remain true even if a credential is valid.
In practice, stronger designs narrow the blast radius with a combination of controls:
- Separate CUI traffic from general corporate access instead of routing everything through one flat tunnel.
- Use conditional access, device posture checks, and MFA to reduce who can connect.
- Apply least privilege at the application, server, and data layer, not only at the VPN edge.
- Log and review access to CUI systems so audit evidence shows who reached what, when, and why.
- Scope privileged administration separately from user access, especially where service accounts or automation touch CUI systems.
This matters because VPN credentials are often shared across more resources than the original approval intended. NHI Management Group notes that only 5.7% of organisations have full visibility into their service accounts, which shows how quickly hidden access paths undermine scoping. That risk is reinforced in the Ultimate Guide to NHIs and the 52 NHI Breaches Analysis, both of which show that excessive reach and weak visibility are recurring failure modes.
Security teams should treat the VPN as a transport mechanism, not a control boundary. The control boundary has to exist where data, systems, and identities intersect, with evidence that access is intentionally limited. These controls tend to break down when legacy remote-access designs still expose broad internal networks because the resulting network adjacency makes resource-level containment difficult to prove.
Common Variations and Edge Cases
Tighter remote-access control often increases operational overhead, requiring organisations to balance CMMC evidence quality against user convenience and administrative complexity. That tradeoff becomes visible in hybrid environments, contractor-heavy environments, and organisations that depend on legacy remote administration tools.
Current guidance suggests that three patterns need extra care. First, third-party support often requires temporary access that should be scoped per ticket or per session, not by permanent VPN membership. Second, admins and automation should use separate paths because privileged access is harder to justify if the same tunnel reaches both CUI and non-CUI services. Third, split-tunnel exceptions can be acceptable in some architectures, but only if the organisation can still prove that CUI resources remain isolated and monitored.
This is also where current best practice is still evolving. There is no universal standard that says every VPN must be replaced, but there is broad agreement that broad network access is a poor substitute for demonstrable control boundaries. The Ultimate Guide to NHIs — Key Challenges and Risks is useful here because it highlights why visibility and privilege discipline matter when access paths multiply. The practical test is simple: if the assessor can traverse from remote access to CUI without seeing a clear, enforced boundary, the design is not ready.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST CSF 2.0, NIST SP 800-63, NIST Zero Trust (SP 800-207) and NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST CSF 2.0 | PR.AC-4 | Broad VPN access often exceeds least-privilege access boundaries. |
| NIST SP 800-63 | AAL2 | CMMC remote access expectations depend on stronger authentication assurance. |
| NIST Zero Trust (SP 800-207) | Zero Trust requires resource-level enforcement, not trust from the VPN boundary. | |
| OWASP Non-Human Identity Top 10 | NHI-03 | Broad VPNs often mask over-privileged service and automation identities. |
| NIST AI RMF | GOV-3 | Readiness depends on governance that defines and evidences control boundaries. |
Inventory non-human accounts and reduce their reach before expanding remote access.
