Communications monitored and controlled at system boundaries

CMMC 2.0 SC.L1-3.13.1 (NIST 800-171r2 3.13.1) requires that communications are monitored and controlled at the external boundary of systems containing FCI. Without rate limiting or request filtering on API endpoints — particularly authentication routes — brute-force credential stuffing attacks succeed unchecked. CWE-799 (Improper Control of Interaction Frequency) and OWASP A05 (Security Misconfiguration) both name boundary control gaps as exploitable. A login endpoint with no rate limit and no logging allows thousands of credential attempts per minute, making any account with a weak password reachable within seconds.

Add rate limiting to all API endpoints. Use a Redis-backed limiter for production scale — in-memory rate limiters reset on cold starts and are unsuitable for multi-instance deployments:

// lib/rate-limit.ts
import { Ratelimit } from '@upstash/ratelimit'
import { Redis } from '@upstash/redis'
export const authRateLimit = new Ratelimit({
  redis: Redis.fromEnv(),
  limiter: Ratelimit.slidingWindow(5, '60 s'),
  analytics: true,
})

// app/api/auth/login/route.ts
export async function POST(req: Request) {
  const ip = req.headers.get('x-forwarded-for') ?? '127.0.0.1'
  const { success } = await authRateLimit.limit(ip)
  if (!success) {
    return Response.json(
      { error: 'Too many login attempts. Try again in 60 seconds.' },
      { status: 429, headers: { 'Retry-After': '60' } }
    )
  }
  // Log the attempt for boundary monitoring
  console.log(JSON.stringify({ event: 'auth_attempt', ip, ts: new Date().toISOString() }))
  // ... proceed with login
}

Vercel and Cloudflare WAF rules provide additional boundary controls at the hosting layer — configure them in addition to application-level rate limiting.