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Fix Unrestricted Resource Consumption in Astro

Unrestricted Resource Consumption (CWE-400) in Astro usually hits during Server-Side Rendering (SSR) or within API routes. If you're parsing large JSON payloads, performing uncapped loops based on user input, or failing to implement rate limiting, an attacker can trivially trigger a Denial of Service (DoS) by exhausting CPU or memory. In serverless environments, this translates directly to a 'Denial of Wallet' attack. Stop trusting the client to be reasonable.

The Vulnerable Pattern

// src/pages/api/generate-report.ts
import type { APIRoute } from 'astro';

export const POST: APIRoute = async ({ request }) => {
// VULNERABILITY: No payload size limit and no input validation
const body = await request.json();


// VULNERABILITY: User-controlled loop count allows CPU exhaustion
const results = [];
for (let i = 0; i < body.iterations; i++) {
results.push(complexCalculation(body.data));
}


return new Response(JSON.stringify({ results }), {
status: 200,
headers: { ‘Content-Type’: ‘application/json’ }
});
};

The Secure Implementation

To secure Astro endpoints, you must implement defensive coding at the entry point. First, validate the 'Content-Length' header to reject massive payloads before the server attempts to parse them into memory. Second, never use user-supplied values directly in loops or recursion; use a 'Math.min()' constraint to enforce a hard ceiling on resource usage. Finally, for production, wrap these routes in middleware that implements rate limiting (using Redis or a similar store) to prevent automated scripts from hammering your SSR engine.

// src/pages/api/generate-report.ts
import type { APIRoute } from 'astro';

const MAX_ITERATIONS = 50;
const MAX_PAYLOAD_SIZE = 1024 * 50; // 50KB


export const POST: APIRoute = async ({ request }) => {
// 1. Check Content-Length header before parsing body
const contentLength = parseInt(request.headers.get(‘content-length’) || ‘0’);
if (contentLength > MAX_PAYLOAD_SIZE) {
return new Response(‘Payload too large’, { status: 413 });
}


try {
const body = await request.json();


// 2. Strict Input Validation
const iterations = Math.min(Math.max(0, Number(body.iterations) || 0), MAX_ITERATIONS);

if (!body.data || typeof body.data !== 'string') {
  return new Response('Invalid Data', { status: 400 });
}

const results = [];
for (let i = 0; i < iterations; i++) {
  results.push(complexCalculation(body.data));
}

return new Response(JSON.stringify({ results }), {
  status: 200,
  headers: { 'Content-Type': 'application/json' }
});


} catch (e) {
return new Response(‘Malformed JSON’, { status: 400 });
}
};

System Alert • ID: 7501
Target: Astro API
Potential Vulnerability

Your Astro API might be exposed to Unrestricted Resource Consumption

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

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