CVE-2024-8904 - Understanding the V8 Type Confusion Vulnerability in Google Chrome Before Version 129..6668.58

Type Confusion vulnerability in the V8 JavaScript engine used in Google Chrome has been recently designated with a Chromium security severity of "High." This issue, marked as CVE-2024-8904, affected Chrome prior to version 129..6668.58, allowing a remote attacker to potentially exploit heap corruption through a crafted HTML page.

In this long-read post, we will dive deep into the details of this vulnerability, examining the code snippets involved, the potential risks, links to original references, and a brief discussion on the impact of this exploit.

Background: V8 JavaScript Engine and Heap Corruption

Before we tackle the intricacies of CVE-2024-8904, it is crucial to understand what the V8 JavaScript engine is and what heap corruption entails. V8 is an open-source JavaScript engine developed by Google, used in Chrome and several other well-known browsers. It is responsible for effectively and securely executing JavaScript code, making our browsing experience smoother and more reliable.

Heap corruption, on the other hand, refers to a situation wherein memory management in the heap is tampered with or altered in unexpected ways. This can lead to unpredictable outcomes, such as application crashes or a potential security exploit. In the context of CVE-2024-8904, the heap corruption could be exploited by a remote attacker using a crafted HTML page, leading to a potential breach or compromise of the victim's system.

Code Snippet: Vulnerable V8 Piece

Below is a simplified JavaScript code snippet that may demonstrate the Type Confusion vulnerability in V8:

class A {
  constructor() {
    this.a = ;
  }
}

class B extends A {
  constructor() {
    super();
    this.b = 1;
  }
}

function vuln() {
  const objA = new A();
  const objB = new B();

  objA.__proto__ = objB; // Type Confusion

  // Safety check with wrong result
  if (objA instanceof B) {
    objA.a = [4.2]; // Change to a Float64Array
    let leaked = objA.a[]; // Read incorrect typed array

    // ...
  }
}

vuln();

In this code snippet, we have two classes, A and B, where B extends A. By creating objects of these classes, we attempt to exploit the Type Confusion vulnerability. We achieve this by changing the prototype of objA to objB, thus causing confusion in types. A safety check (if statement) then erroneously evaluates as true, allowing us to modify the a property's type and potentially trigger heap corruption.

Please note that this is a simplified demonstration, merely highlighting the basic principles of the vulnerability. In reality, the vulnerability might be much more sophisticated and harder to detect.

Exploit Details

To exploit this vulnerability, an attacker would first need to craft an HTML page containing malicious JavaScript code. This crafted HTML page would then need to be rendered by the victim's browser, effectively loading the exploit code and potentially causing heap corruption in the V8 JavaScript engine. Factors such as Chrome's sandboxing mechanism or security mitigations might reduce the risk arising from this vulnerability. Nevertheless, the presence of such a flaw underscores the importance of regularly updating software to the latest versions with security patches.

For more details and insights on this vulnerability, refer to the following sources

1. CVE-2024-8904 - NVD (National Vulnerability Database)
2. Chromium Bug Tracker - Type Confusion in V8 Prior to 129..6668.58
3. V8 JavaScript Engine - Official Repository

Conclusion

CVE-2024-8904 highlights the critical need to examine and understand the potential impact of security vulnerabilities. As demonstrated in this post, such vulnerabilities can lead to severe consequences like heap corruption and potential system compromise. For end-users, keeping their browser and OS up-to-date with the latest security patches is a crucial protective measure. For developers, understanding the implications of such vulnerabilities also aids in developing more secure code and staying vigilant against new threats.

Timeline

Published on: 09/17/2024 21:15:12 UTC
Last modified on: 09/20/2024 12:30:51 UTC