VNX-GQL-002 – GraphQL Query Batching or No Depth Limit (DoS)

Overview

This rule detects Apollo Server configured with allowBatchedHttpRequests: true. Query batching allows a client to send an array of multiple GraphQL operations in a single HTTP request. Without this being paired with strict per-operation rate limiting and query depth/complexity controls, an attacker can send hundreds of complex operations in a single request, completely bypassing any HTTP-layer rate limiting and causing denial of service through CPU or database connection exhaustion.

GraphQL’s flexible query language creates DoS attack surfaces that HTTP-layer controls cannot address alone. Both HTTP-level batching and deeply nested single queries can exhaust server resources — this rule targets the former; depth/complexity limits address the latter.

Severity: Medium | CWE: CWE-770 – Allocation of Resources Without Limits or Throttling | CAPEC: CAPEC-469 – HTTP DoS

OWASP ASVS v4: V13.4.1 — Verify that a query allowlist or a combination of depth limiting and amount limiting is used to prevent GraphQL DoS as a result of expensive, nested queries.

Why This Matters

GraphQL’s flexible query structure creates unique denial-of-service opportunities that HTTP-layer rate limiting cannot fully address:

Batching amplification: With allowBatchedHttpRequests: true, an attacker sends a JSON array of 50 operations in a single HTTP request. Your load balancer counts one request; your server executes 50 expensive resolver chains. Standard rate limiting (requests per minute per IP) is bypassed entirely.

Nested query exhaustion: A maliciously nested query can cause exponential resolver execution even without batching:

# This single query can lock up your event loop or exhaust your DB connection pool
{
  user {
    friends {
      friends {
        friends {
          friends {
            posts {
              comments {
                author {
                  friends { id }
                }
              }
            }
          }
        }
      }
    }
  }
}

Real-world GraphQL DoS attacks have taken production services offline within seconds because the default GraphQL execution engine has no built-in query complexity limits. The OWASP GraphQL Cheat Sheet explicitly calls out both batching and depth limiting as required controls.

What Gets Flagged

// FLAGGED: batching enabled without compensating controls
const server = new ApolloServer({
  typeDefs,
  resolvers,
  allowBatchedHttpRequests: true,  // <-- flagged
});

Remediation

Disable Batching (Recommended Default)

Most applications do not need HTTP-level query batching. The default in Apollo Server is false:

// SAFE: batching disabled (default behaviour)
const server = new ApolloServer({
  typeDefs,
  resolvers,
  // allowBatchedHttpRequests omitted — defaults to false
});

Add Query Depth and Complexity Limits (Apollo Server / graphql-js)

Install graphql-depth-limit and a complexity analysis library, then apply them as validation rules:

// Install: npm install graphql-depth-limit graphql-cost-analysis
import depthLimit from 'graphql-depth-limit';
import costAnalysis from 'graphql-cost-analysis';

const server = new ApolloServer({
  typeDefs,
  resolvers,
  allowBatchedHttpRequests: false,
  validationRules: [
    depthLimit(7),
    costAnalysis({ maximumCost: 1000, defaultCost: 1 }),
  ],
});

Graphene (Python)

Use the built-in depth_limit_validator from graphene.validation:

from graphene_django.views import GraphQLView
from graphene.validation import depth_limit_validator

class DepthLimitedGraphQLView(GraphQLView):
    def get_validation_rules(self):
        return [depth_limit_validator(max_depth=10)]

# In urls.py
urlpatterns = [
    path('graphql/', DepthLimitedGraphQLView.as_view(graphiql=False)),
]

graphql-java

Use MaxQueryDepthInstrumentation and MaxQueryComplexityInstrumentation:

GraphQL graphQL = GraphQL.newGraphQL(schema)
    .instrumentation(new ChainedInstrumentation(Arrays.asList(
        new MaxQueryDepthInstrumentation(10),
        new MaxQueryComplexityInstrumentation(200)
    )))
    .build();

graphql-java ships with a default maximum depth of 20. Set this explicitly to a value appropriate for your schema rather than relying on the default.

gqlgen (Go)

// In graph/schema.resolvers.go — add complexity limits via handler config
import "github.com/99designs/gqlgen/graphql/handler/extension"

srv := handler.NewDefaultServer(generated.NewExecutableSchema(cfg))
srv.Use(extension.FixedComplexityLimit(300))

If You Must Enable Batching

If batching is required for a trusted internal client (e.g., a BFF layer), apply all of the following compensating controls:

Count each operation in a batch separately against rate limits
Set a maximum number of operations per batch (e.g., no more than 10)
Apply query depth and complexity limits to every operation in the batch
Restrict batching to authenticated sessions only

const server = new ApolloServer({
  typeDefs,
  resolvers,
  allowBatchedHttpRequests: true,
  validationRules: [depthLimit(7), costAnalysis({ maximumCost: 500 })],
  plugins: [
    {
      async requestDidStart({ request }) {
        // Reject batches larger than 10 operations
        if (Array.isArray(request.body) && request.body.length > 10) {
          throw new Error('Batch size limit exceeded');
        }
      },
    },
  ],
});