GraphQL Security Check (CWE-400)

What this checks

Protects against GraphQL-specific attack vectors: unbounded query depth that causes exponential resolver execution, introspection left enabled in production (exposing the full schema to attackers), and batch/alias attacks that bypass rate limiting.

Vulnerable patterns

• GraphQL server constructed with no depth-limit or cost-analysis validation rule
• Deeply nested query allowed because no maximum-depth rule rejects it before resolver execution
• Alias batching that repeats a credential-accepting field many times in one request, bypassing per-HTTP-request rate limits
• Introspection left enabled in production, exposing the full schema to unauthenticated callers

Fix immediately

Flag the vulnerable code and explain the risk. Translate the principles below to the language and framework of the audited file — use that stack's documented validation rule, plugin, or middleware API; do not roll your own.

For each finding, establish these properties:

1. Query depth is capped at a small fixed value (typically 5–10) by a validation rule or middleware that runs before resolver execution. Unbounded depth lets a single query trigger exponential resolver work.
2. Total query cost is bounded. Either a cost-analysis layer that assigns weights to fields and rejects over-budget queries, or alias/field-count limits — the goal is that a single request cannot do unbounded work regardless of depth. Alias batching bypasses per-request rate limits unless this is enforced.
3. Introspection is disabled in production. Leaving it on exposes the full schema — including deprecated fields, admin types, and hints for targeted attacks — to anyone who can hit the endpoint. Gate it on an environment flag.
4. Every credential-accepting mutation (login, passwordReset, mfaVerify) has a rate limit that survives alias batching — apply per operation, not per HTTP request, so a thousand aliased login selections count as a thousand attempts.

Verification

• Query depth is limited to a fixed maximum (typically 5-10) via a validation rule or middleware
• Introspection is disabled in production environments
• Batch/alias attacks are mitigated by cost analysis, alias limits, or per-operation rate limiting

References

• CWE-400 (Uncontrolled Resource Consumption)
• CWE-200 (Exposure of Sensitive Information)