In April 2024, Google released a security patch for a serious vulnerability tracked as CVE-2024-3833. This flaw affects the WebAssembly engine in Google Chrome and puts users at risk of remote code exploitation via corrupted JavaScript objects in a malicious HTML page. In this post, we'll demystify how this vulnerability works, who could exploit it, and what you should do. Whether you’re a developer, a security enthusiast, or just a curious user, stick around—it's simple, exclusive, and clear.

CVE-2024-3833 is described officially as

> Object corruption in WebAssembly in Google Chrome prior to 124..6367.60 allowed a remote attacker to potentially exploit object corruption via a crafted HTML page. (Chromium security severity: High)
> Chromium Issue 333423249

Translation:
A carefully created (malicious) website could take advantage of a bug in Chrome’s WebAssembly to mess with how JavaScript “objects” are managed in memory. This error could allow an attacker to execute code on your computer—simply by making you visit a web page.

Why Does WebAssembly Matter Here?

WebAssembly is a tech built into browsers so they can run code written in languages other than JavaScript (like C, C++, or Rust). It’s fast, but working close to the metal also means bigger risks if mistakes are made in memory handling.

How Does Object Corruption Happen?

Object corruption occurs when internal JavaScript or WebAssembly objects are put into a bad state. Attackers try to do this so they can:

Run arbitrary code on your system (at worst)

In this case, the bug was present in versions before Chrome 124..6367.60. It involved incorrect handling of objects created or manipulated through WebAssembly, allowing their data to be treated as something else, leading to an exploit.

Proof-of-Concept Exploit (Educational Only!)

Let’s look at a simplified code snippet similar to how an attacker could try to identify the vulnerability (this will NOT actually exploit the bug, but demonstrates the idea):

<script>
  // Sample vulnerable code pattern

  // Create a simple WebAssembly module
  const wasmCode = new Uint8Array([
      x00,x61,x73,x6d, // WASM_BINARY_MAGIC
      x01,x00,x00,x00, // WASM_BINARY_VERSION
      // ... (rest of a tiny, valid module)
  ]);
  
  // Compile and instantiate that WebAssembly
  WebAssembly.instantiate(wasmCode.buffer).then(result => {
      // Try to create side-effects or strange object accesses
      let leakedObj = result.instance.exports;
      leakedObj.someProperty = 12345;

      // This next line *could* misinterpret object boundaries in vulnerable versions
      for (let i = ; i < 10000; i++) {
          leakedObj['prop' + i] = i;
      }

      // In a true exploit, the next steps would spray memory and trigger corruption
  });
</script>

> Note: Actual exploit code is much more complex and dangerous; this is for demonstration only.

Where To Learn More

- Google Chrome Release Notes (124..6367.60)
- Chromium Security Tracker for CVE-2024-3833
- WebAssembly Official Site

Final Word

Vulnerabilities in browsers are serious—especially when memory corruption is involved. Thanks to Google’s quick response, most users are now safe from CVE-2024-3833. The lesson? Always keep your browser up to date!

Stay safe, and let’s break down complex security—one CVE at a time.


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Timeline

Published on: 04/17/2024 08:15:10 UTC
Last modified on: 08/01/2024 13:56:42 UTC