Why do excessive permissions create so much risk in Zero Trust programmes?

Why This Matters for Security Teams

zero trust changes the trust model, but it does not automatically change what an identity can do. When permissions are too broad, a single compromised service account, API key, or workload identity can still reach systems, data stores, and control planes that were never needed for its job. That is why overprivilege remains one of the fastest ways to turn a contained incident into an enterprise-wide one.

NHI Management Group’s Ultimate Guide to NHIs notes that 97% of NHIs carry excessive privileges, and that aligns with what Zero Trust programmes often miss: network segmentation is only half the problem. The other half is entitlement sprawl inside the identity plane. NIST’s NIST SP 800-207 Zero Trust Architecture frames trust as a continuous decision, but that decision is undermined when access is already too broad at the identity layer.

In practice, many security teams discover overprivilege only after an attacker has already used a legitimate identity to pivot, enumerate, or exfiltrate rather than through intentional privilege design.

How It Works in Practice

Excessive permissions create risk because they increase the number of valid actions an identity can perform after compromise. In a Zero Trust model, every request should be evaluated on context, but if the identity has broad standing access, the policy engine can only limit so much. The practical goal is to pair Zero Trust with least privilege so that the identity is constrained before the request ever reaches a sensitive target. The OWASP Non-Human Identity Top 10 and NHIMG’s Top 10 NHI Issues both reinforce that over-entitled NHIs are a common root cause of lateral movement and data exposure.

For most programmes, the operational sequence looks like this:

• Inventory every non-human identity, including service accounts, workload identities, API keys, and automation tokens.
• Map each identity to a specific task or service boundary, not to a broad organisational role.
• Remove unused privileges first, then shrink remaining permissions to the minimum resource, action, and environment required.
• Replace standing access with just-in-time elevation where possible, especially for privileged automation paths.
• Continuously re-evaluate access against runtime context, such as workload, source, time, and purpose.

In stronger implementations, workload identity helps prove what the workload is, while policy-as-code decides what it may do at request time. That is the difference between static trust and enforced constraint. Current guidance suggests combining identity-bound controls with short-lived credentials, because long-lived permissions are difficult to detect, review, and revoke at machine speed. These controls tend to break down in legacy environments with shared service accounts and hard-coded credentials because the identity cannot be cleanly tied to a single workload or action.

Common Variations and Edge Cases

Tighter privilege controls often increase operational overhead, requiring organisations to balance security gain against deployment friction and automation complexity. That tradeoff is especially visible in environments with high deployment frequency, third-party integrations, or shared infrastructure where access patterns are not stable.

There is no universal standard for how fine-grained entitlement modelling must be yet, but best practice is evolving toward context-aware and time-bound access rather than broad roles. In some estates, RBAC is still useful for coarse grouping, but it should not be the final control for autonomous systems or high-value NHIs. Zero Trust is also less effective when the underlying asset model is unclear, because the policy engine cannot reliably distinguish between a legitimate spike in activity and an attacker chaining permissions.

For practitioner guidance, the key question is not whether an identity has access, but whether it has more access than its current task requires. NHIMG’s research on Ultimate Guide to NHIs for key challenges and risks shows how quickly unbounded access becomes systemic. If an organisation cannot answer who owns an NHI, what it can touch, and when that access is reviewed, Zero Trust becomes a label rather than a control. In that condition, excessive permissions remain the easiest path for abuse because the system is technically authenticated but operationally overexposed.

Related resources from NHI Mgmt Group

• Why do service account secrets create so much risk in zero trust architecture?
• Why do valid credentials still create so much risk in zero trust environments?
• Why does interoperability create identity risk if it is not paired with trust rules?
• Why do non-human identities create more audit risk than human accounts?