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Fix Lack of Resources & Rate Limiting in Go Fiber

Go Fiber is built for speed, but its default configuration is a playground for resource exhaustion. Without explicit rate limiting and request body constraints, an attacker can trigger a Denial of Service (DoS) by flooding the event loop or saturating memory with oversized payloads. To harden a Fiber app, you must implement the limiter middleware and enforce strict timeout/size policies.

The Vulnerable Pattern

package main

import “github.com/gofiber/fiber/v2”


func main() {
app := fiber.New()


// VULNERABLE: No rate limiting, no request size limits, no timeouts.
// An attacker can spam this endpoint to exhaust file descriptors and CPU.
app.Post("/upload", func(c *fiber.Ctx) error {
    return c.SendString("Data received")
})

app.Listen(":3000")


}

The Secure Implementation

The fix involves two layers: Server-level constraints and Middleware-level throttling. First, the `fiber.Config` is updated with `BodyLimit` to prevent memory-based DoS and `ReadTimeout` to close 'Slowloris' style connections. Second, the `limiter` middleware is injected into the stack. It uses an in-memory store (default) to track the request count per IP. When the threshold (50 requests/min) is hit, Fiber short-circuits the request and returns a 429 Too Many Requests status code, protecting the underlying business logic from being overwhelmed.

package main

import (
“time”
“github.com/gofiber/fiber/v2”
“github.com/gofiber/fiber/v2/middleware/limiter”
)


func main() {
// Hardening the server configuration
app := fiber.New(fiber.Config{
ReadBufferSize: 4096,
BodyLimit:      2 * 1024 * 1024, // Limit body to 2MB
ReadTimeout:    5 * time.Second,
})


// Implementing the Rate Limiter middleware
app.Use(limiter.New(limiter.Config{
	Max:          50,              // Max 50 requests
	Expiration:   1 * time.Minute, // Per minute per IP
	KeyGenerator: func(c *fiber.Ctx) string {
		return c.IP() // Track by IP address
	},
	LimitReached: func(c *fiber.Ctx) error {
		return c.Status(429).JSON(fiber.Map{
			"error": "Rate limit exceeded. Slow down, hacker.",
		})
	},
}))

app.Post("/upload", func(c *fiber.Ctx) error {
	return c.SendString("Securely processed")
})

app.Listen(":3000")


}

System Alert • ID: 5027
Target: Go Fiber API
Potential Vulnerability

Your Go Fiber API might be exposed to Lack of Resources & Rate Limiting

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

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