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Framework Security

Is Fastify Secure? Security Features, Risks, and Hardening

Yes, Fastify is generally secure when configured correctly. Here is what you need to know about its built-in protections, common vulnerabilities, and how to harden it for production.

Built-in Security Features

Built-in JSON Schema validation for requests and responses
Plugin encapsulation prevents cross-plugin data leakage
Automatic serialization prevents prototype pollution in responses
Built-in request body size limits

Common Vulnerabilities

Misconfigured CORS allowing overly broad origins
Bypassing schema validation with content-type manipulation
Insecure deserialization in custom content-type parsers
Unprotected routes due to missing preHandler hooks

Hardening Checklist

1Define strict JSON schemas for all route inputs and outputs
2Use @fastify/helmet for security headers
3Implement @fastify/rate-limit for API rate limiting
4Configure @fastify/cors with specific allowed origins
5Use @fastify/csrf-protection for form-based routes
6Register authentication plugins at the correct encapsulation scope
7Enable ajv strict mode for schema validation
8Use @fastify/secure-session for signed cookie sessions

Read the complete Fastify security guide

In-depth blog post with code examples and best practices

Official Fastify security documentation

Frequently Asked Questions

Is Fastify secure?

Yes, Fastify is generally secure when configured correctly. It includes built-in protections like built-in json schema validation for requests and responses. However, common misconfigurations and development patterns can introduce vulnerabilities.

What are the main security risks with Fastify?

The most common Fastify security risks include misconfigured cors allowing overly broad origins, bypassing schema validation with content-type manipulation, insecure deserialization in custom content-type parsers.

How do I harden Fastify for production?

Key hardening steps: Define strict JSON schemas for all route inputs and outputs. Use @fastify/helmet for security headers. Implement @fastify/rate-limit for API rate limiting. Run a security check on your domain to identify specific issues.

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