BOLA in GraphQL APIs: Emerging Risks and How to Mitigate Them

By Clinton Nwezeaku
on April 14, 2025

As GraphQL continues to revolutionize API design with its flexibility and efficiency, it also introduces a new landscape of security concerns. One such critical vulnerability is Broken Object Level Authorization (BOLA), which has consistently topped the OWASP API Security Top 10. While BOLA is a well-documented issue in RESTful APIs, its presence in GraphQL APIs poses unique risks due to the query language’s dynamic and deeply nested structure.

In this blog, we explore how BOLA manifests in GraphQL environments, its implications for data security, and practical ways to detect and mitigate it.

What Is BOLA in GraphQL?

Broken Object Level Authorization (BOLA), also known as Insecure Direct Object Reference (IDOR), occurs when an API fails to properly enforce access controls on objects, allowing unauthorized users to access data they shouldn’t. In a GraphQL context, this vulnerability becomes even more potent due to the following:

Nested queries: Attackers can access related objects within a single query.
Custom resolvers: Developers may overlook proper authorization checks in individual resolvers.
Predictable object identifiers: IDs passed in queries can be guessed or incremented.

Example:

				
					query {
  user(id: "123") {
    name
    email
    orders {
      id
      amount
    }
  }
}

If the API doesn’t verify whether the requester has permission to access user ID 123 and their related orders, it is vulnerable to BOLA.

Why GraphQL Is Especially Prone to BOLA

1. Flexible Query Structure

GraphQL allows clients to specify exactly what data they want, leading to complex nested queries. This increases the attack surface.

2. Resolver-Level Authorization

Unlike REST where endpoint-level checks are common, GraphQL requires checks in each resolver. One missed check can expose sensitive data.

3. Reusability and Shared Logic

Resolvers are often reused across queries and mutations. Improper scoping can lead to access leaks.

4. Lack of Granular Monitoring

Traditional API gateways and logging mechanisms might not provide visibility into GraphQL query behavior, making it harder to detect abuse.

Real-World Impact of BOLA in GraphQL

Several high-profile data breaches have involved insecure GraphQL implementations. Attackers have exploited predictable user IDs and missing authorization in resolvers to enumerate user data, financial records, and internal messages.

In multi-tenant applications, BOLA can allow attackers to access data belonging to other tenants, causing massive breaches of confidentiality.

How to Identify BOLA in GraphQL APIs

1. Threat Modeling and Query Mapping

Start by cataloging all GraphQL queries and mutations. Understand which objects are exposed and how identifiers are used.

2. Manual Testing with GraphQL Clients

Use tools like GraphiQL, Altair, or Insomnia to craft queries with varied object IDs. Try:

Accessing objects owned by other users.
Exploring nested relationships for lateral movement.

3. Role-Based Testing

Test access with different user roles (guest, user, admin) to uncover privilege escalation paths.

4. Authorization Audits in Resolvers

Review resolver code to ensure authorization logic is consistently applied. Missing or inconsistent checks are a red flag.

5. Use of Security Linters and Static Analysis Tools

Integrate GraphQL-specific linters in your CI pipeline to catch common security anti-patterns.

Mitigating BOLA in GraphQL APIs

1. Enforce Authorization in Every Resolver

Each resolver must verify that the requesting user has permission to access the requested object.

Example in JavaScript (Apollo Server):

				
					const resolvers = {
  Query: {
    user: async (_, { id }, { user }) => {
      const targetUser = await getUserById(id);
      if (targetUser.id !== user.id && !user.isAdmin) {
        throw new Error("Unauthorized");
      }
      return targetUser;
    }
  }
};

2. Implement Field-Level Authorization

Go beyond resolver-level checks. Sensitive fields like email, ssn, or roles may require additional conditions.

3. Use Opaque or Hashed Identifiers

Avoid exposing raw database IDs. Use UUIDs, hashed values, or indirect references that cannot be guessed.

4. Use GraphQL Middleware for Authorization

Leverage tools like graphql-shield to apply rule-based access control globally.

5. Rate Limiting and Query Complexity Analysis

Use query depth limiting, throttling, and allow-listing to minimize risk from deep introspection or enumeration attacks.

6. Logging and Monitoring

Log GraphQL query patterns, especially those involving object identifiers. Monitor for repeated access attempts to sensitive object IDs.

Best Practices for Long-Term GraphQL Security

Design with Principle of Least Privilege: Only expose necessary data and objects.
Document Security Requirements: Make authorization rules explicit in API documentation.
Security Unit Testing: Write unit tests for access control logic in resolvers.
Regular Security Audits: Conduct code reviews with a focus on authorization.
Security Headers and TLS: Ensure secure transport and disable introspection in production.

Conclusion

As GraphQL adoption continues to surge, so does the need for robust security practices tailored to its unique architecture. Broken Object Level Authorization remains one of the most severe and easily exploitable vulnerabilities in GraphQL APIs. By incorporating strict authorization checks at every layer of your GraphQL implementation, developers and security teams can stay ahead of attackers and protect sensitive data.

Securing GraphQL isn’t just about performance and flexibility—it’s about trust. Stay vigilant, review your access controls, and build APIs that are both powerful and secure.

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BOLA in GraphQL APIs: Emerging Risks and How to Mitigate Them

What Is BOLA in GraphQL?