When Your Next.js App Just... Dies: The Sneaky Stack Overflow Bug That's Been Crashing Servers

Source: Dev.to

So, picture this: you’re working on your Next.js app, everything’s running smooth, your tests are passing, code review looks good. You deploy to production and… boom. Your server just dies. No error logs. No catchable exceptions. Just exit code 7 and your app is gone.

Sound familiar? You’re not alone. This exact scenario has been haunting full‑stack developers for months, and it all comes down to a sneaky bug in Node.js that was fixed in January 2026. Let’s dig into what went wrong and how to protect your apps.

What Even Happened?

There was a critical vulnerability in Node.js (CVE‑2025‑59466) that could crash your entire application when deep recursion met a little thing called async_hooks. And the worst part? Your error handlers couldn’t catch it.

This wasn’t just a theoretical bug either. It was actively affecting:

• React Server Components
• Next.js applications
• Every major APM tool (Datadog, New Relic, Dynatrace, Elastic APM, OpenTelemetry)

Literally any app using AsyncLocalStorage – basically everyone building modern full‑stack apps.

The Real‑World Problem

You’re building a typical full‑stack app with Next.js. Maybe you’re processing some user‑submitted JSON, parsing nested objects, or traversing a deep data structure. Normal stuff, right?

// Looks innocent enough, right?
async function processNestedData(data, depth = 0) {
  if (depth > 100) return; // You even added a safety check!

  if (typeof data === 'object') {
    for (let key in data) {
      await processNestedData(data[key], depth + 1);
    }
  }

  return data;
}

Now imagine a malicious user (or just bad data) sends you something like this:

// Deeply nested object that looks like: {a: {a: {a: {a: ... }}}}
let evil = {};
let current = evil;
for (let i = 0; i  {
  try {
    causeChaos(100000); // This will overflow the stack
    console.log('This never prints');
  } catch (error) {
    console.log('Neither does this'); // Bug: catch block never executes
  }
});

• Before the patch: Process crashes immediately, no error caught.
• After the patch: Error is properly caught and handled.

The Fix (And How to Protect Yourself)

The Node.js team released patches for versions 20.x, 22.x, 24.x, and 25.x. Even with the patch, you shouldn’t rely on stack‑overflow error handling for security or availability.

1. Update Node.js IMMEDIATELY

# Check your version
node --version

# Update to patched versions:
# v20.x → v20.18.2 or later
# v22.x → v22.13.2 or later
# v24.x → v24.0.2 or later
# v25.x → v25.3.0 or later

2. Validate Input Depth

Don’t let users control how deep your recursion goes. Add real checks:

function safeProcessData(data, maxDepth = 50) {
  function process(obj, currentDepth = 0) {
    if (currentDepth > maxDepth) {
      throw new Error(`Data nesting exceeds maximum depth of ${maxDepth}`);
    }

    if (typeof obj !== 'object' || obj === null) {
      return obj;
    }

    // Process object properties recursively
    for (const key in obj) {
      obj[key] = process(obj[key], currentDepth + 1);
    }
    return obj;
  }

  return process(data);
}

3. Guard Async Contexts

If you need AsyncLocalStorage, wrap only the minimal code that truly requires it, and keep recursion depth checks outside that context.

const { AsyncLocalStorage } = require('async_hooks');
const als = new AsyncLocalStorage();

function handleRequest(req, res) {
  // Validate / sanitize input first
  const safeBody = safeProcessData(req.body);

  // Only then run the async‑local context
  als.run(new Map(), () => {
    // Your business logic that relies on async hooks
    doSomethingAsync(safeBody).then(...).catch(...);
  });
}

4. Monitor Process Exit Codes

Add a listener for the exit event to log unexpected termination codes:

process.on('exit', (code) => {
  if (code !== 0) {
    console.error(`Process exited with code ${code}`);
    // Send alert / restart logic here
  }
});

TL;DR

• Bug: Deep recursion + async_hooks caused Node.js to exit with code 7 (CVE‑2025‑59466).
• Impact: Crashed Next.js, React Server Components, and any app using AsyncLocalStorage.
• Fix: Update Node.js to the patched versions released Jan 13 2026.
• Mitigation: Validate input depth, limit async‑hook usage, and monitor exit codes.

Stay safe, keep your dependencies fresh, and never trust unchecked recursion again! 🚀

1️⃣ Safe Recursive Processing

function safeProcessData(data, maxDepth = 50) {
  function process(obj, currentDepth = 0) {
    if (currentDepth > maxDepth) {
      throw new Error('Maximum depth exceeded');
    }

    if (Array.isArray(obj)) {
      return obj.map(item => process(item, currentDepth + 1));
    }

    if (obj && typeof obj === 'object') {
      const result = {};
      for (const key in obj) {
        result[key] = process(obj[key], currentDepth + 1);
      }
      return result;
    }

    return obj;
  }

  return process(data);
}

// Use it like this
app.post('/api/data', (req, res) => {
  try {
    const safeData = safeProcessData(req.body, 50);
    // Process safeData…
    res.json({ success: true });
  } catch (error) {
    res.status(400).json({ error: error.message });
  }
});

2️⃣ Use Iteration Instead of Recursion

When possible, flatten your approach:

// Recursive traversal
function recursiveSum(arr) {
  if (!Array.isArray(arr)) return arr;
  return arr.reduce((sum, item) => sum + recursiveSum(item), 0);
}

// Iterative approach
function iterativeSum(arr) {
  const stack = [...arr];
  let sum = 0;

  while (stack.length) {
    const item = stack.pop();
    if (Array.isArray(item)) {
      stack.push(...item);
    } else {
      sum += item;
    }
  }

  return sum;
}

3️⃣ Add Request Size Limits

Don’t let huge payloads reach your code:

const express = require('express');
const app = express();

// Limit JSON payload size
app.use(
  express.json({
    limit: '100kb',
    verify: (req, res, buf, encoding) => {
      // Additional validation if needed
      if (buf.length > 100000) {
        throw new Error('Request too large');
      }
    },
  })
);

4️⃣ Monitor Your Deployment

Set up proper monitoring so you catch crashes:

// Process exit handlers
process.on('exit', code => {
  console.error(`Process exiting with code: ${code}`);
  // Log to your monitoring service
});

process.on('uncaughtException', error => {
  console.error('Uncaught Exception:', error);
  // Send to error tracking (Sentry, etc.)
  process.exit(1);
});

🧪 Testing Your Fix

A simple test to verify your app is protected:

// test/stack-overflow.test.js
const request = require('supertest');
const app = require('../app');

describe('Stack Overflow Protection', () => {
  it('should reject deeply nested JSON', async () => {
    // Create evil deeply nested object
    let evil = { data: 'value' };
    let current = evil;

    for (let i = 0; i  {
    const normalData = {
      user: {
        profile: {
          settings: {
            theme: 'dark',
          },
        },
      },
    };

    const response = await request(app)
      .post('/api/process')
      .send(normalData)
      .expect(200);

    expect(response.body.success).toBe(true);
  });
});

📚 The Bigger Picture

This bug shows why full‑stack development in 2026 is wild:

• Frontend – React, Next.js doing server‑side rendering
• Backend – Node.js APIs handling user data
• Cloud – Providers running code in opaque environments
• APM – Tools trying to track everything

When one tiny piece breaks, the whole stack can crash.

Key lesson: Don’t trust the runtime to save you. Build defensive code from the start.

✅ Quick Checklist for Full‑Stack Devs

Before shipping your next feature:

• Update to the latest Node.js patch version
• Validate input depth on all user data
• Configure request size limits
• Replace recursion with iteration where possible
• Set up error monitoring (Sentry, Datadog, etc.)
• Configure alerts for exit code 7
• Add integration tests covering edge cases
• Perform load testing with malicious payloads

🛠 What This Means for Your Stack

🏁 Final Thoughts

Bugs happen—even in battle‑tested tech like Node.js. The important thing is staying informed and protecting your apps proactively.

• Validate inputs.
• Write defensive code.
• Test edge cases.
• Monitor everything.

And, for the love of JavaScript, keep your Node.js version up to date!