Why do VPNs create risk even when they use strong encryption?

VPN encryption protects the transport path, but it does not prove that the connected subject should be trusted broadly inside the environment. Once connected, the tunnel can become a conduit for lateral movement if the account, device, or workload is compromised. Strong transport security is useful, but it is not the same as least-privilege authorisation.

Why This Matters for Security Teams

VPNs are often treated as a trust boundary, but encryption only protects traffic in transit. It does not verify whether the endpoint is healthy, whether the account is compromised, or whether the connected subject should have broad internal access after authentication. That distinction matters because modern intrusion paths often start with a valid connection and then move sideways through systems that were never intended to be reachable.

This is the same structural weakness called out in Zero Trust guidance from the NIST Cybersecurity Framework 2.0 and in NHIMG research on how over-permissive identities expand attack paths. NHIs are especially relevant because VPNs can carry service credentials, API access, and admin tooling just as easily as human logins. When those identities are over-privileged, the tunnel becomes a transport layer for misuse, not a control layer for trust. The Ultimate Guide to NHIs — Why NHI Security Matters Now notes that NHIs outnumber human identities by 25x to 50x in modern enterprises, which is why broad network access can quickly become disproportionate access.

In practice, many security teams encounter VPN-driven lateral movement only after an account, device, or secret has already been abused.

How It Works in Practice

A strong VPN creates an encrypted tunnel, but the real security question is what happens after the tunnel opens. If the connected user or workload is trusted too broadly, the VPN effectively grants an internal starting point for reconnaissance, credential harvesting, and tool chaining. That is why current guidance increasingly favors Zero Trust principles, where access is evaluated per request rather than assumed from network location.

For human users, that means combining VPN access with device posture checks, MFA, role scoping, and segmentation. For NHIs, it means treating the identity itself as the control point. The Top 10 NHI Issues and the Ultimate Guide to NHIs — Key Challenges and Risks both reinforce the same operational pattern: long-lived secrets, excessive privilege, and weak visibility turn connectivity into exposure. A safer design uses short-lived credentials, workload identity, and explicit authorization at the service or application layer rather than trusting whatever sits behind the tunnel.

• Restrict VPN users to the minimum reachable network segments.
• Pair VPN access with conditional checks on device health, user risk, and location.
• Use short-lived secrets and rotate credentials aggressively for NHIs.
• Prefer workload identity and policy decisions at request time over static network trust.
• Monitor for unusual east-west traffic, credential reuse, and privilege escalation after login.

These controls tend to break down in flat networks with legacy applications because the VPN becomes the easiest path to everything inside.

Common Variations and Edge Cases

Tighter VPN restrictions often increase operational overhead, requiring organisations to balance developer convenience and incident response speed against reduced blast radius. That tradeoff is real, especially where remote administration, third-party support, or hybrid infrastructure still depends on network-layer reachability.

Best practice is evolving, but there is no universal standard that says a VPN should disappear entirely. In some environments it remains a practical transport mechanism, especially for legacy systems or regulated operations. The risk appears when teams confuse encryption with trust and fail to add identity-aware controls on top. That is why ZTNA-style access, bastion segmentation, and context-aware authorization are increasingly preferred for administrative paths. For NHIs, the same logic applies: if a service account or automation token can reach critical systems through the VPN, then the tunnel has become a privilege amplifier.

Security teams should also watch for exceptions such as vendor support tunnels, emergency break-glass access, and CI/CD runners that connect through VPN concentrators. These cases need tighter scoping, logging, and explicit expiration. The OWASP NHI Top 10 is useful here because it frames identity risk around misuse, not just credential theft.

When VPN access is treated as a blanket trust signal, the encryption stays strong while the internal attack surface grows anyway.

Related resources from NHI Mgmt Group

• Why do OAuth and OpenID Connect integrations create IAM risk even when they reduce password use?
• Why do secrets create disproportionate risk in NHI environments?
• When does shift left create more risk than it reduces?
• Why do AI agents create new risk even when they are short-lived?