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Summary

CVE-2024-3914 is a critical use-after-free vulnerability discovered in the V8 JavaScript engine, impacting Google Chrome versions prior to 124..6367.60. This flaw allows a remote attacker to corrupt the heap and potentially execute arbitrary code just by tricking a victim into visiting a specially crafted web page. The vulnerability is categorized as high severity by the Chromium security team.

In this post, we'll break down what use-after-free means, show a simplified code snippet, discuss the exploitation path, and share original references for deeper research.

What is a Use-After-Free in V8?

A use-after-free (UAF) bug happens when a program continues to use a memory location after it has been freed or deallocated. In the context of V8 (Chrome’s JavaScript engine), this can occur when certain JavaScript operations free up internal objects but Chrome still references them — leading to unpredictable and unsafe behavior.

Because JavaScript runs inside your browser, such vulnerabilities are highly valuable to attackers who want to hijack browsers and gain deeper system access.

CVE-2024-3914: Technical Explanation

In the case of CVE-2024-3914, a flaw exists in the way V8 engine manages object lifetimes. By carefully manipulating JavaScript objects and triggering garbage collection, a remote attacker could free an object and trick V8 into referencing the now-invalid memory — leading to a heap corruption.

To exploit this, an attacker lures a victim to a crafted webpage that executes the exploit JavaScript code. This code orchestrates the right conditions for use-after-free and may let the attacker run their own code with the privileges of the user’s browser.

Code Example (Simplified)

*Please note this is for educational and informational purposes only.*

Below is a simplified snippet (not the full exploit) demonstrating the basic principle

// This code simulates a use-after-free pattern in V8, not the actual exploit.
let arr = new Array(100).fill(1);

function triggerGC() {
    for (let i = ; i < 10000; i++) {
        let temp = new Array(100);
    }
}

function uafDemo() {
    // Step 1: Reference arr
    let ref = arr;
    // Step 2: Remove the strong reference and trigger GC
    arr = null;
    triggerGC();
    // Step 3: Use 'ref' after arr is freed
    console.log(ref[]); // In some buggy V8 code paths, this could crash or hijack
}

uafDemo();

This is not a working exploit, but it shows how releasing an object and triggering garbage collection can set up use-after-free in V8 under certain edge cases.

In a real attack, the exploit code is much more complex, involving memory spraying and reliable triggering of the bug.

Special JavaScript executes: The site runs crafted code triggering V8’s vulnerable code path.

3. Heap corruption occurs: Attacker manages to reuse freed memory, often filling it with their malicious data.
4. Arbitrary code execution: The manipulated memory is run, possibly giving the attacker control of the browser.

Update Chrome immediately: Ensure you are running version 124..6367.60 or later.

2. Enable automatic updates: Chrome usually updates itself, but you can check via chrome://settings/help.
3. Practice safe browsing: Only visit websites you trust and be careful with links from emails or messages.

Chromium Security Advisory:

Chrome Releases: Stable Channel Update for Desktop (2024-04-16)

CVE Details:

CVE-2024-3914 at NVD

Project Zero (Google):

V8 Exploitation Techniques

V8 Exploit Writeups:

- How to Exploit a V8 Use-after-free (book chapter)

Conclusion

CVE-2024-3914 is a high-risk, real-world bug that highlights the complexity of modern JavaScript engines and the importance of timely browser updates. While attackers have already demonstrated skills exploiting these use-after-free bugs, users and administrators can stay protected by keeping browsers patched.

Stay safe, keep Chrome up to date, and be careful browsing unfamiliar websites.

*This post is written for educational awareness and helps highlight the importance of patching security vulnerabilities. Never attempt to exploit software without explicit authorization.*

Timeline

Published on: 04/17/2024 18:15:16 UTC
Last modified on: 07/03/2024 02:06:52 UTC