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Fix Insecure API Management in Fastify

API sprawl and loose management are the primary vectors for BOLA (Broken Object Level Authorization) and DoS. In Fastify, failing to enforce strict schema validation, global rate limiting, and proper authentication hooks turns your microservices into a playground for automated exploitation. Stop leaking internal state and start enforcing strict contract-driven security.

The Vulnerable Pattern

const fastify = require('fastify')();

// VULNERABLE: No rate limiting, no schema validation, no authentication fastify.get(‘/api/data/:id’, async (request, reply) => { const { id } = request.params; // Direct database query without input sanitization or ownership check const data = await db.query(SELECT * FROM sensitive_data WHERE id = ${id}); return data; });

fastify.listen({ port: 3000 });

The Secure Implementation

1. Schema Validation: Use Fastify's built-in AJV integration to enforce strict input/output types, preventing injection and data oversharing. 2. Rate Limiting: Register @fastify/rate-limit to mitigate brute-force and DoS attacks. 3. Security Headers: Use @fastify/helmet to set essential HTTP headers. 4. Auth Hooks: Implement preHandler hooks to ensure all endpoints are authenticated by default. 5. Response Serialization: Explicitly define response schemas to filter out sensitive database fields like passwords or internal IDs.

const fastify = require('fastify')();
const rateLimit = require('@fastify/rate-limit');
const helmet = require('@fastify/helmet');

fastify.register(helmet); fastify.register(rateLimit, { max: 100, timeWindow: ‘1 minute’ });

const getDataSchema = { params: { type: ‘object’, properties: { id: { type: ‘integer’ } } }, response: { 200: { type: ‘object’, properties: { public_info: { type: ‘string’ } } } } };

fastify.get(‘/api/data/:id’, { schema: getDataSchema, preHandler: [fastify.authenticate] }, async (request, reply) => { // Using parameterized queries and validating ownership const data = await db.query(‘SELECT public_info FROM sensitive_data WHERE id = $1 AND owner_id = $2’, [request.params.id, request.user.id]); if (!data) return reply.code(404).send({ error: ‘Not Found’ }); return data; });

System Alert • ID: 2250
Target: Fastify API
Potential Vulnerability

Your Fastify API might be exposed to Insecure API Management

74% of Fastify apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.

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