Google Chrome is one of the world’s most-used browsers. But beneath that smooth interface, complex tech is always running, and sometimes – things go wrong. In October 2022, a critical bug, CVE-2022-3723, was discovered in Chrome’s JavaScript engine, V8. This bug is scary: it lets attackers run malicious code on your computer just by luring you to a webpage.

Today, we’re diving into CVE-2022-3723, showing how it works, the background, and a *real* proof-of-concept exploit — using clear language anyone can follow.

1. What Is CVE-2022-3723?

CVE-2022-3723 is a “type confusion” bug in the V8 JavaScript engine, the part of Chrome that runs JavaScript code (what powers most web pages). If an attacker tricks you into visiting a malicious website, they can exploit this bug to corrupt memory (heap corruption) — potentially letting them run programs of their choice on your computer.

Severity: HIGH (remote code execution possible)

- Original Advisory: Google's Stable Channel Update

2. Understanding Type Confusion In V8

Type confusion is when a program assumes a piece of data is one thing, but it’s actually another. In most programming languages this is prevented, but in JavaScript engines, to make things fast, some “assumptions” are made.

In V8, the JavaScript engine, some optimizations may fail to check data types strictly. That can lead to situations where, for example, a string is treated as a number, or an object as an array — that’s “type confusion.” This can break all bounds of logic and memory safety.

Let’s see a simple (non-dangerous) code example of type confusion

function confuse(obj) {
  if (typeof obj === 'number') {
    // The engine might optimize and assume "obj" is always a number.
    return obj + 1;
  }
  // But what if it's actually an object?
  return obj.someProperty;
}

console.log(confuse({someProperty: 123})); // May cause confusion if the engine optimizes wrong!

Attackers craft data and code to make V8 treat data *unsafely* — allowing them to read, write, and even execute malicious code in your browser.

3. The Details – How Attackers Exploit It

CVE-2022-3723 was discovered by Clément Lecigne of Google's Threat Analysis Group on October 25, 2022, "in the wild" (meaning: real attacks were happening).

This lets attackers write or read memory they shouldn't have access to (heap corruption).

- With this control, attackers craft data that will let them run their own code (called remote code execution).

The original bug was in how V8 handled certain JavaScript operations on objects and arrays, failing to check types in all cases.

4. Step-by-Step Exploit Example (Code)

Here’s a simplified, educational proof of concept. (This is for info only—running against new Chrome versions is safe, but *don’t use for hacking!*)

// Array with doubles
let arr = [1.1, 2.2, 3.3, 4.4];

// Crafted object to trigger confusion
function confuse_type(obj) {
    let a = [obj, 2.2, 3.3];
    // Evil code: tricks the engine into thinking "a" is just numbers
    a[] = 1.1; // Overwrites the first slot with a double
    return a;
}

// Now, try to mess up the types!
for (let i = ; i < 10000; ++i) {
    confuse_type({}); // "Warm up" with objects
}

// Next call: engine may wrongly "assume" the first element is always an object
let corrupted = confuse_type(1.1);

// Try to access more than allowed!
console.log(corrupted[]); // Is it 1.1? Or dangerous memory?

// In real exploits, next steps use this confusion to overwrite function pointers or object addresses!

Then, you throw in a *number* instead of an object.

- The JIT compiler (to make JavaScript run fast) gets *confused* about what type of data is being handled.

This opens the door to heap corruption.

Real attackers use more complex code to get stable arbitrary read/write, and then run shellcode. (See references below for detailed technical exploits.)

5. Was I Vulnerable? What To Do?

If you updated Chrome after October 27, 2022, you’re safe.
If you’re running an older version, upgrade *immediately*. This bug was found in active attacks (“zero-day”), so it’s a big deal.

Go to menu → Help → About Google Chrome

If you see 107..5304.87 or higher, you’re protected.

6. References & Further Reading

- Google Chrome Release Notes
- NIST NVD CVE-2022-3723 Entry
- Project Zero (V8 Exploits)
- Writeup: “Exploiting V8 Type Confusion for day RCE”
- Official Chrome Issue 1369108 (Not yet public; check for updates)

Final Thoughts

Type confusion bugs like CVE-2022-3723 show just how dangerous memory errors can be in even the most secure browsers. Thankfully, Chrome’s team patches these rapidly — but always keep your browser up to date.

*If you’re interested in browser security, try building little experiments with older V8 builds in a safe, virtual environment to learn more. But never attack live browsers!*

Timeline

Published on: 11/01/2022 23:15:00 UTC
Last modified on: 11/10/2022 00:15:00 UTC