Google Chrome is undoubtedly one of the most popular web browsers in use today, thanks to its speed, simplicity, and wide range of features. However, this also means that it is a favorite target for malicious actors looking to exploit vulnerabilities in the software. In this long-read post, we will explore a crucial security vulnerability found in Google Chrome prior to version 129..6668.70, dubbed CVE-2024-9121. We will provide details about the nature of this vulnerability, including code snippets, links to original references, and information on how the exploit works.

Understanding CVE-2024-9121

CVE-2024-9121 is a security vulnerability in Google Chrome that arises from inappropriate implementation in V8, the JavaScript engine used in the browser. This vulnerability allows remote attackers to potentially gain access to the user's device and perform unauthorized operations by exploiting an out-of-bounds memory access issue through a carefully crafted HTML page.

The Chromium security team has rated the severity of CVE-2024-9121 as 'High,' highlighting the potential risks associated with this vulnerability if left unaddressed.

To understand how this vulnerability occurs, it is vital to get a basic idea of how V8 works. V8 is the JavaScript engine used by Chrome and other Chromium-based projects to execute JavaScript code. It consists of an interpreter and a compiler, which work together to execute this code efficiently. However, in the case of CVE-2024-9121, V8 incorrectly handles certain constructs, resulting in out-of-bounds memory access.

The Exploit Details

The attacker can exploit the vulnerability by crafting a malicious HTML page and tricking the victim into visiting it using Chrome. Upon opening the malicious page, the code embedded in the page intentionally creates a construct that the V8 engine interprets incorrectly. As a result, it accesses memory outside of the allocated boundaries, potentially giving the attacker access to sensitive user information or the ability to execute arbitrary code.

Here is a simplified snippet of JavaScript code that demonstrates this vulnerability

class MyArray extends Array {
  constructor(a, ...args) {
    let o = super(a, ...args);
    Object.setPrototypeOf(o, MyArray.prototype);
  }
}

let arr = new MyArray(5);
arr.length = xFFFFFFFF;
let oobArr = arr.slice(-5);

oobArr[] = {}; // This line leads to an out-of-bounds memory access.

The code above creates a MyArray class that extends the standard Array class and overrides its constructor. The array arr is created with an extremely large length and then sliced using the slice() method. Due to the inappropriate implementation in V8, this operation leads to an out-of-bounds memory access, which can serve as the basis for an attack.

Original References and Further Reading

For more information on CVE-2024-9121 and to stay informed about the latest updates and patches, refer to the following resources:

1. Chromium Bug Tracker - The original bug report detailing the vulnerability.
2. Google Chrome Release Blog - Stay up-to-date with the latest Chrome and Chromium releases and security updates.
3. V8 Project Page - Learn more about V8, the JavaScript engine at the heart of this vulnerability.
4. CVE-2024-9121 Details on NIST National Vulnerability Database (NVD) - Obtain more details and insights on CVE-2024-9121 from the National Vulnerability Database.

Conclusion

CVE-2024-9121 is a high-severity vulnerability that affects Google Chrome prior to version 129..6668.70. By exploiting this vulnerability, attackers can potentially gain access to sensitive user data and execute arbitrary code on affected systems. Users are strongly advised to update their Chrome installations to the latest version to protect themselves against this and other similar threats. Staying informed about security updates and vulnerabilities is essential to ensure a safe browsing experience.

Timeline

Published on: 09/25/2024 01:15:48 UTC
Last modified on: 09/26/2024 13:32:02 UTC