Exploring and investigating the vulnerabilities of a GraphQL implementation

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Exploring and investigating the vulnerabilities of a GraphQL implementation requires a combination of manual testing, automated tools, and understanding of both GraphQL’s specification and the underlying application stack (backend language, framework, database). Below are 50 in-depth tasks, organized into categories, that you should consider during your GraphQL security assessment.

🛠️ RECONNAISSANCE

  1. Locate the GraphQL endpoint Common paths: /graphql, /gql, /api/graphql.

  2. Determine the HTTP methods allowed Usually POST, sometimes GET. Misconfigured servers may allow dangerous methods.

  3. Fingerprint the GraphQL engine/framework E.g., Apollo Server, Graphene, express-graphql, etc., by checking response headers, error messages, or introspection output.

  4. Check for introspection availability Query using __schema { types { name } } to see if schema introspection is enabled.

  5. Determine if GraphiQL or GraphQL Playground is exposed Access to these UIs can aid attackers by providing autocomplete and docs.

  6. Check for rate-limiting or throttling Send multiple queries or batched requests to determine limits.

  7. Assess authentication requirements Can you access the endpoint anonymously?

  8. Determine if CORS policy is permissive Misconfigured CORS could allow cross-origin exploitation.

  9. Check HTTP headers (security-related) Cache-Control, Content-Type, X-Frame-Options, CSP, etc.

  10. Look for debug info in error messages Stack traces, SQL queries, file paths.

🔍 SCHEMA ENUMERATION

  1. Use introspection to dump full schema Use tools like graphql-voyager, InQL, or GraphQL Voyager.

  2. Identify object types and input types Understanding data structure is crucial for injection attacks.

  3. Enumerate mutations and queries Look for dangerous operations like create, update, delete.

  4. Check for custom scalars (e.g., Email, URL, JSON) These might have lenient or flawed validation logic.

  5. Check for file upload endpoints (Upload scalar) These may expose arbitrary file write vulnerabilities.

  6. Identify nested types and relationships Useful for crafting deep queries (e.g., for DoS).

  7. Analyze directive usage E.g., @include, @skip, and custom directives.

  8. Search for deprecated fields May still be functional but unmaintained/insecure.

  9. Map out access control annotations E.g., @auth, @admin, @private.

  10. Compare schemas for different user roles Use various tokens to compare visibility.

⚙️ INPUT VALIDATION / INJECTION TESTING

  1. Test for GraphQL Injection Inject into fields/variables: Example:

    query { user(id: "1) { id name }") }

  2. Test for classic SQL injection via GraphQL E.g., { user(id: "1' OR '1'='1") { id } }

  3. Test for NoSQL injection (MongoDB/DocumentDB) E.g., passing JSON-like structures into parameters.

  4. Check for command injection in mutation fields

  5. Try broken input types E.g., sending string where int is expected.

  6. Fuzz all input arguments and variables Use fuzzing tools with wordlists for edge-case handling.

  7. Try bypassing validation using aliases GraphQL supports field aliases. Use them to craft confusing or deceptive queries.

  8. Check for over-permissive enums Some may expose internal application states or modes.

  9. Manipulate complex input types (InputObject, Lists) Submit malformed arrays or nested objects.

  10. Check for HTTP Parameter Pollution in query variables

🔐 AUTHORIZATION / ACCESS CONTROL

  1. Test access control on all queries and mutations Remove JWT, use lower-privileged roles.

  2. Access other users’ data via IDOR E.g., { user(id: 2) { email } }

  3. Try unauthorized role mutation (e.g., promote to admin)

  4. Check object-level access control (OLAC) Nested queries may bypass top-level ACL.

  5. Tamper with JWT (alg:none, expired token, etc.)

  6. Check if permissions are enforced on resolvers Look for field-level permission leaks.

📉 DOS / ABUSE

  1. Perform a query depth attack Deeply nested query to exhaust backend recursion limits.

  2. Send large batched queries GraphQL allows batching multiple queries in a single request.

  3. Exploit alias overloading Use many aliases to repeat the same field hundreds of times.

  4. Send large query payloads to stress parsing

  5. Try cyclic queries (fragments referencing each other) Some servers may not properly handle recursion.

  6. Check for logging DoS (via verbose queries)

📦 MISC / MISCONFIGURATION

  1. Test CSRF if GraphQL is accessible over GET

  2. Check for file uploads vulnerabilities (if supported) Abuse Upload scalar to try overwriting or injecting.

  3. Try SSRF via user-supplied URLs in inputs

  4. Check if subscriptions are enabled (WebSockets) Misused subscriptions can lead to info leaks or persistent sockets.

  5. Abuse query complexity limits Test if @complexity directives or query limits are enforced.

  6. Check if deprecated operations are still active

  7. Check GraphQL federation or remote schemas Misconfigured federated services can leak internal APIs.

  8. Inspect implementation source code (if available) Look for resolver-level flaws, custom directives, access control logic.

🧰 Tools to Aid in the Assessment

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