You know Zero Trust is covering vendor access when third-party identities follow the same approval, session recording, and entitlement review process as internal privileged users. If vendors still use separate support channels or standing access exceptions, the programme is only partially enforced.
Why This Matters for Security Teams
Vendor access is the fastest way to find out whether zero trust is real or just a label. If third-party users still bypass normal identity proofing, approval, monitoring, or entitlement review, the control plane is split in two: one path for internal staff and another for everyone else. That creates a blind spot precisely where privileged access is most exposed. NIST’s NIST SP 800-207 Zero Trust Architecture is explicit that trust should be continuously evaluated, not granted by network location or legacy exception.
NHI Management Group research shows why this matters operationally: 92% of organisations expose NHIs to third parties, raising supply chain security concerns, and 90% of IT leaders say properly managing NHIs is essential for a successful zero-trust implementation. That combination is telling. If vendor identities are not handled as privileged identities with full lifecycle controls, the organisation is not applying Zero Trust to the actual risk surface. The relevant guidance in the Ultimate Guide to NHIs and the 52 NHI Breaches Analysis shows that exception-based access is where governance often degrades first. In practice, many security teams discover vendor exceptions only after an incident review exposes them.
How It Works in Practice
To verify that Zero Trust actually covers vendor access, treat the vendor like any other privileged identity and test the workflow end to end. The question is not whether a vendor has credentials, but whether those credentials are issued, constrained, observed, and revoked under the same policy logic as internal users. That means approval should be tied to a business justification, access should be time bound, session activity should be recorded where feasible, and entitlement reviews should include vendor accounts in the same recertification cycle as employee admin access.
In a working model, the vendor path should include:
- Identity proofing and sponsor approval before access is granted.
- Least-privilege entitlements mapped to a named system, ticket, or task.
- Short-lived access with automatic expiry, not open-ended standing permission.
- Session logging or proxy-based monitoring for privileged actions.
- Periodic access review with removal of dormant or overbroad vendor entitlements.
Current guidance suggests that if a vendor can still use a separate support channel, shared admin account, or manual exception process, Zero Trust is only partially enforced. That is especially true where vendors connect through legacy VPNs, maintain long-lived API keys, or use delegated access that is not visible in the primary IAM and PAM stack. The OWASP Non-Human Identity Top 10 is useful here because vendor access often behaves like a non-human workload when it relies on tokens, service accounts, or machine-mediated approvals. The Guide to SPIFFE and SPIRE is also relevant when organisations want stronger workload identity patterns for automation and third-party integrations.
The practical test is simple: can the security team trace a vendor request from approval to session to revocation without leaving the Zero Trust control plane? These controls tend to break down when vendor access is delivered through legacy remote-support tooling because the activity is invisible to entitlement governance and session controls.
Common Variations and Edge Cases
Tighter vendor control often increases operational overhead, requiring organisations to balance faster support access against stronger assurance. That tradeoff is real, especially for critical infrastructure, incident response retainers, or highly specialised OEM support where delayed access can affect uptime. Best practice is evolving, and there is no universal standard for every vendor scenario, but the control objective stays the same: no vendor should receive broader or longer access than the task requires.
Some environments need differentiated treatment. A vendor with interactive admin access to production systems should face the full approval, session control, and review workflow. A vendor supplying an API integration may need workload identity, scoped tokens, and automated revocation instead of human session recording. A break-glass scenario may justify temporary elevation, but it should still be logged, time-boxed, and reviewed after use. Where organisations rely on shared service accounts, the Zero Trust question becomes harder because accountability is diluted and revocation becomes approximate rather than precise. The Ultimate Guide to NHIs — Key Challenges and Risks is useful for understanding why this breaks down in mixed human and machine access models, while the Ultimate Guide to NHIs — Standards helps anchor the governance discussion.
The clearest signal is not policy language but revocation reality: if access can be removed immediately, reviewed centrally, and attributed to a named vendor workflow, Zero Trust is being applied. If not, the programme still depends on exceptions.
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 Zero Trust (SP 800-207) and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST Zero Trust (SP 800-207) | Principle 1 | Zero Trust requires continuous evaluation of vendor trust, not network-based exceptions. |
| OWASP Non-Human Identity Top 10 | NHI-01 | Vendor access often uses non-human or delegated identities that need full lifecycle control. |
| NIST CSF 2.0 | PR.AC-4 | Vendor access must be managed through access approval and entitlement governance. |
Place vendor accounts in the same access review and approval workflow as internal privileged users.
