In June 2023, a major security vulnerability—CVE-2023-3079—was found affecting Google Chrome’s V8 JavaScript engine. This flaw, rated high severity, allowed attackers to cause heap corruption by tricking the browser to misuse memory with a specially crafted web page. Before Chrome version 114..5735.110, users were at risk of remote exploitation. Let’s break down how this type confusion happens, walk through a simplified exploit, and share key resources.

What is Type Confusion?

Type confusion is a security bug that happens when a software program allocates memory for one type of object but later treats it as a different type. In dynamic languages like JavaScript, this can cause the V8 engine to misinterpret data in memory, potentially leading to memory corruption.

If an attacker can craft a JavaScript snippet so V8 mistakes an object’s type, they might read or write arbitrary data in memory, opening a path to code execution.

How Did CVE-2023-3079 Happen?

The bug targeted Chrome’s V8 engine, which converts JavaScript into machine code for fast execution. In some cases, V8’s optimization routines incorrectly assumed the type of JavaScript objects, failing to double-check during JIT (just-in-time) compilation. This left an opening for type confusion.

Subsequently, code writes or reads beyond what’s expected.

This memory confusion often allows access to memory locations not intended for JavaScript, enabling heap corruption.

Code Snippet: How Type Confusion Could Look

Here’s a simplified proof-of-concept (PoC), inspired by public research—not an active exploitation tool, just an education example:

// WARNING! Do NOT run untrusted code in your browser.

function confuse(victim) {
    let arr = [1.1, 2.2, 3.3];
    let objArr = [{}, {}, {}];

    function trigger(o) {
        // Force type confusion via optimization
        arr[] = o; // Suppose V8 optimizes this as all doubles
        return arr[];
    }

    for (let i = ; i < 10000; ++i) {
        trigger(1.1); // Warm up with numbers (doubles)
    }

    // Now pass an object, hope for type confusion
    let corrupted = trigger(victim);

    // If there's a bug, 'corrupted' points to an object, but interpreted like a double
    console.log(corrupted);
}

// This could result in V8 confusing object pointers and doubles
confuse({evil: true});

Note: In real attacks, the code would be way more complex, leveraging detailed knowledge of V8’s memory model and gaining primitive read/write abilities.

Exploit Details

CVE Identifier: CVE-2023-3079  
Component: V8 JavaScript Engine  
Impacted Versions: Google Chrome < 114..5735.110  
Exploitability: Remote - simple webpage (HTML/JS)

When loaded in a vulnerable browser, the crafted code triggers V8 to mix up object types.

- This results in heap memory corruption, and possibly further exploitation, such as sandbox escape or code execution.

Google’s Official Advisory:  
- Chromium Bug 1442762

PSA: Chromecast, Edge, Brave, and any Chromium-based browsers may be affected.


> “Type confusion in V8 in Google Chrome prior to 114..5735.110 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.”  
(Release Notes)

Public Writeup/PoC:  
- Project Zero writeup  
- NVD Entry  

How Was it Fixed?

Google patched the issue in Chrome 114..5735.110 by tightening V8’s type checks and modifying the optimization logic to prevent misuse of type information.

2023-06-05: Chrome stable channel updated.

What should you do?

Conclusion

CVE-2023-3079 is a classic example of a high-severity, remotely exploitable bug in web browsers’ JavaScript engines. With type confusion leading to heap corruption, even a simple visit to a malicious page could have exposed users to code execution risks.

Stay secure:

Resources for More:  
- Chrome Security Updates
- Google Project Zero Blog
- CVE-2023-3079 NVD


*Exclusive tip:* If you’re into browser research or want to understand JavaScript engine risks, keep an eye on JIT optimization topics—this is where many modern attacks start. And always run your browser in the sandboxed mode it ships with!

Timeline

Published on: 06/05/2023 22:15:00 UTC
Last modified on: 06/12/2023 16:47:00 UTC