GraphQL Security: Introspection, Excessive Queries and Authorization Risks

GraphQL is a flexible API approach that lets the client query exactly the data it needs from a single endpoint. That flexibility is powerful but brings risks distinct from REST: schema exposure, resource exhaustion via nested queries, and field-level authorization. This article covers GraphQL-specific risks and their defences.

Introspection: exposing the schema

GraphQL’s “introspection” lets a client query the entire schema (types, fields, mutations). Useful in development, but left open in production it hands an attacker a complete map of the API surface.

• Recommendation: disable introspection in production or restrict it to authenticated developers. This does not replace fixing real flaws, but it hides the attack-surface map.

Excessive/nested queries: resource exhaustion

GraphQL’s flexibility means a single query can be very deep or very wide. A malicious client can send a very expensive query using nested relationships and overload the server (a form of DoS).

• Query depth limiting.
• Query cost/complexity analysis: assign a cost to each field and reject queries over a budget.
• Mandatory pagination on list fields.
• Rate limiting on the endpoint.

Authorization: field-level control

With a single endpoint, “protect the endpoint” is insufficient; authorization must be applied at the field/type level. Even if a user can access a type, they must not access its sensitive fields (e.g., another user’s email). BOLA/BFLA risks apply in GraphQL too and require field-level checks.

Error messages

Verbose GraphQL error messages can leak internal structure and schema. Simplify error output in production; log internal details only.

Summary

GraphQL’s flexibility brings distinct risks: disable introspection in production, prevent resource exhaustion with depth/complexity limits and rate limiting, apply authorization at the field level rather than the endpoint, and simplify error messages. Together these make the flexibility safe.

Sources: OWASP GraphQL Cheat Sheet, OWASP API Security Top 10.

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