Wildcard expansion is the evaluation of wildcard characters such as * and ? to understand the full scope of access a policy may grant. In IAM analysis, this matters because a compact-looking action or resource pattern can represent a much broader permission boundary than it first appears to humans or tools.
Expanded Definition
Wildcard expansion is the process of resolving pattern characters such as NIST SP 800-53 Rev 5 Security and Privacy Controls into the concrete actions or resources they match. In access analysis, the important question is not how short a statement looks, but how wide the effective permission boundary becomes once the pattern is interpreted.
In IAM, wildcard expansion is often discussed in policy review, entitlement audit, and least-privilege validation. A policy that appears narrow at a glance can become broad after expansion, especially when a wildcard applies to verbs, resource paths, regions, environments, or role names. Industry usage is still evolving in some toolchains, but the core idea is stable: human readers should evaluate the full match set, not the abbreviated syntax.
A common boundary mistake is to treat wildcard characters as harmless shorthand rather than as a permission amplifier. That misunderstanding is especially costly when the same pattern is reused across many accounts, roles, or automated workflows.
Examples and Use Cases
Practitioners encounter wildcard expansion in reviews where a single pattern may authorize far more than intended. The practical test is whether the resolved set still fits the original business purpose.
- A cloud policy allows a broad action pattern, and expansion reveals that it includes administrative operations the reviewer did not expect.
- An object-storage path wildcard matches multiple buckets or prefixes, turning a scoped request into multi-tenant exposure.
- A CI/CD role uses a resource glob that also matches temporary build artifacts, logs, and deployment targets.
- An IAM report flags a condition where one compact-looking statement grants permissions across all regions rather than a single environment.
- A secrets or certificate workflow uses pattern matching for names, and expansion shows that rotation or retrieval applies to more identities than planned.
The tradeoff is convenience versus precision: wildcards reduce policy sprawl, but they also make it easier for reviewers to miss unintended breadth unless the matched scope is explicitly enumerated during analysis.
Security Implications
Wildcard expansion matters because it can hide excessive privilege, unintended resource reach, and policy collisions. The security issue is not the character itself; it is the gap between the compact syntax and the actual authorization surface after resolution.
When expansion is not understood, teams may approve access that covers entire classes of resources, operations, or environments. That can widen blast radius after compromise, enable lateral movement through overbroad service permissions, and make detection harder because the policy appears narrower than the runtime effect. NHIMG research shows that 97% of NHIs carry excessive privileges, increasing unauthorised access and broadening the attack surface.
Operational symptoms often include permission reviews that miss inherited matches, audit tools that under-report matched resources, and incident investigations that discover a much larger set of accessible objects than the original ticket implied.
Domain and Governance Relevance
Wildcard expansion is especially important in NHI governance because machine identities frequently rely on reusable patterns in roles, service principals, tokens, and automation policies. Those patterns can scale safely only when inventory, ownership, and scope review are strong enough to keep the resolved permission set visible.
For non-human identities, the practical question is whether the wildcard is bounded by lifecycle controls and periodic review. If the pattern reaches across many workloads or environments, the failure is not just overpermission. It becomes a governance problem involving unclear ownership, weak review discipline, and a larger revocation burden when the identity or secret must be changed. NHIMG’s Ultimate Guide to NHIs is a useful reference when you need broader context on lifecycle, visibility, rotation, and offboarding for machine identities.
Wildcard expansion therefore sits at the point where policy syntax meets operational trust. In mature environments, it should be treated as something to enumerate, validate, and periodically recheck, not as a cosmetic shorthand.
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 and MITRE ATT&CK address the attack and risk surface, while CIS Controls v8, NIST CSF 2.0 and NIST Zero Trust (SP 800-207) set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| CIS Controls v8 | 6 — Access Control Management | Wildcard expansion exposes the real scope of access rights and review needs. |
| Recommendation — Review expanded patterns to remove unintended access and enforce least privilege. | ||
| NIST CSF 2.0 | PR.AC — Identity Management, Authentication, and Access Control | Expanded wildcards change the effective access boundary and authorization scope. |
| Recommendation — Validate resolved permissions so policy intent matches actual access granted. | ||
| OWASP Non-Human Identity Top 10 | NHI-02 — Secrets and Credential Management | Machine identities often rely on wildcarded policies that can overgrant access. |
| Recommendation — Enumerate wildcard matches for NHI credentials and shrink overbroad access paths. | ||
| NIST Zero Trust (SP 800-207) | 5.2 — Least Privilege Access | Wildcarded permissions can violate zero trust by broadening implicit trust. |
| Recommendation — Constrain wildcarded permissions so each access path is explicitly justified. | ||
| MITRE ATT&CK | T1098 — Account Manipulation | Adversaries abuse overbroad patterns to expand effective account capabilities. |
| Recommendation — Hunt for overbroad policy patterns that let attackers widen compromised access. | ||
Related resources from NHI Mgmt Group
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Reviewed and updated by the NHIMG editorial team on September 9, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
