Søren Johanson

GraphQL adoption has grown massively among startups in the last few years, yet most API security guidance remains firmly REST-centric. This creates a dangerous blind spot as GraphQL introduces unique security challenges that traditional API protection strategies simply weren't designed to address.

There’s a steep learning curve for most engineers as concepts such as field-level authorisation aren’t found in REST APIs.

Why GraphQL security differs from REST

Unlike REST APIs with their fixed endpoints and predictable data returns, GraphQL provides a single endpoint where clients can request precisely the data they need. This flexibility is powerful, but it introduces novel attack vectors:

Query complexity exploitation - Attackers can craft nested queries that consume excessive server resources
Introspection vulnerabilities - GraphQL's self-documenting nature can reveal sensitive schema information
Resolver-specific weaknesses - Each resolver function presents a potential security boundary to manage

For non-technical founders, understanding these unique challenges is crucial when planning security investments and evaluating development priorities.

Technical implementation guide: Securing your GraphQL layer

Query complexity analysis

GraphQL allows clients to create deeply nested queries that can overload your database and create denial-of-service scenarios. Various libraries exist to implement query complexity analysis, such as graphql-query-complexity.

Authorization in nested relationships

The biggest GraphQL security flaw that I most frequently see is improper authorisation in nested queries:

# Vulnerable query example
query {
  user(id: "current-user") {
    teams {
      projects {
        secretDocuments {  # No authorization check here!
          content
        }
      }
    }
  }
}

Always implement authorisation at each resolver level, not just at the query entry point:

// Secure resolver pattern
const resolvers = {
  User: {
    teams: (parent, args, context) => {
      // Authorization check at the teams level
      if (!isAuthorizedForTeams(context.user, parent.id)) {
        throw new Error('Not authorized');
      }
      return getTeamsForUser(parent.id);
    }
  }
}

Performance-security balancing techniques

GraphQL's flexibility creates unique performance challenges that become security issues:

Implement field-level cost analysis - Assign weights to expensive fields
Use persisted queries - Whitelist approved queries to prevent query injection
Employ depth limiting - Restrict how deep queries can nest to prevent resource exhaustion
Consider resolver-specific rate limiting - Apply limits to particularly expensive operations

Business impact takeaways

GraphQL security failures typically manifest as:

Unexpected server costs from query abuse
Data leakage across tenant boundaries
Slow performance leading to poor user experience
Complete API unavailability during DoS attacks

Properly securing your GraphQL API early prevents these issues from becoming business crises as you scale.

Yours,
Søren

Looking to ensure your GraphQL implementation has robust security guardrails? I provide focused GraphQL security audits for early-stage startups, identifying vulnerabilities before they impact your business. Book a no-obligation consultation to discuss your specific GraphQL security needs.

Securing GraphQL APIs: Avoiding the pitfalls startups miss