A custom claim is an additional data field inserted into a token beyond the standard registered claims. It lets a security team or application encode business-specific attributes, such as department or office status, that are needed for downstream decisions. The claim must be governed carefully because it can influence access control.
Expanded Definition
A custom claim is a non-standard token field used to carry application-specific context that the issuer and consumer both understand. In practice, it extends identity data beyond registered claims such as issuer, audience, subject, and expiry, so downstream services can make decisions using business attributes rather than querying another system on every request.
The boundary matters: a custom claim is not a permission by itself, and it should not be treated as a durable source of truth for volatile state unless the token lifecycle supports that assumption. Common examples include tenant tier, department, device posture, office location, or workflow status. Definitions vary across vendors on how much logic belongs in the token versus the application, so teams should treat custom claims as a design choice, not a universal pattern. The OWASP Non-Human Identity Top 10 is relevant when custom claims are used in machine tokens, because the claim design becomes part of the trust model for automated access.
Examples and Use Cases
Custom claims show up wherever token contents need to reflect business context that standard identity fields do not capture. They are especially common in systems that want fast authorization decisions without an extra lookup on every request.
- A SaaS platform adds a tenant plan claim so the API can enable premium features without a separate entitlement query.
- An enterprise token includes a department claim so internal services can route requests to the correct data domain.
- A workforce portal adds a location or office-status claim to support conditional access and localized policy.
- An automation platform embeds workflow state in a service token so a bot can continue a step without re-authenticating to a database.
- A federated application uses a partner-specific claim when the standard profile does not express a required business attribute.
The trade-off is speed versus freshness. Embedding more context reduces lookups, but it also increases the chance that the token carries stale or overly broad assumptions if the underlying attribute changes before token expiry.
Security Implications
Custom claims matter because they can become authorization inputs, and authorization logic tends to inherit whatever integrity the claim source provides. If the issuer can be influenced, if claim construction is inconsistent, or if consumers trust the claim more than they should, a user or service may gain access that no longer matches policy.
Mismanaged claims also create hidden coupling. A field added for convenience can silently become embedded in several services, making future changes risky and making revocation harder when the business rule changes. In NHI environments, this is especially sensitive because machine-issued tokens can be reused at scale and may carry claims that affect automated access without a human review step. NHIMG research on secrets and machine access shows how quickly exposed credentials are abused, which is why claim-driven automation needs tight control over who can mint, alter, and consume token content. See DeepSeek breach for a concrete example of how exposed credentials and sensitive backend data amplify downstream trust risk.
Observable symptoms include authorization decisions that differ across services, claims that outlive the business state they represent, and audit logs that show token contents being trusted without independent verification. When that happens, the failure is often not the token itself but the assumption that the claim remains valid for the entire token lifetime.
Domain and Governance Relevance
Custom claims sit at the intersection of identity design, authorization policy, and data governance. They are not merely a formatting detail inside a token; they define which attributes are allowed to influence access decisions and which system owns those attributes over time.
For human users, the governance question is whether a claim is authoritative enough to drive access or only suitable for user interface personalization. For non-human identities, the stakes are higher because claims may be consumed by services, pipelines, or agents that act automatically and at machine speed. That means claim provenance, renewal, and revocation become part of the machine identity lifecycle, not just a token-format concern. When claims are used to represent workload context or delegated authority, their correctness directly affects privilege scope, segmentation, and cross-service trust. In that sense, custom claims are one of the places where identity data becomes operational control logic, and the governance model has to be explicit before the claim is widely consumed.
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 |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-02 — Secrets and Credential Management | Custom claims in machine tokens affect how NHIs authenticate and authorize. |
| Recommendation — Restrict token claims to verified machine attributes and reject unauthorised claim sources. | ||
| CIS Controls v8 | 6 — Access Control Management | Claims often drive access decisions and entitlement enforcement. |
| Recommendation — Validate claim-based authorization rules against least-privilege access requirements. | ||
| NIST CSF 2.0 | PR.AA — Identity Management, Authentication, and Access Control | Custom claims shape identity assertions consumed by access control decisions. |
| Recommendation — Document which claims are authoritative inputs to access decisions and review them regularly. | ||
| NIST Zero Trust (SP 800-207) | AC-4 — Dynamic Policy Enforcement | Claims can be evaluated as contextual inputs to policy decisions at request time. |
| Recommendation — Use contextual claim checks to enforce policy without assuming claims remain current. | ||
| MITRE ATT&CK | T1098 — Account Manipulation | Abused claims can alter effective access by changing identity attributes or trust inputs. |
| Recommendation — Hunt for tampered identity attributes that change effective authorization paths. | ||
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
