A critical vulnerability, dubbed CVE-2023-5218, has been uncovered in Site Isolation, a security feature found in Google Chrome web browsers prior to version 118..5993.70. This vulnerability allows a remote attacker to potentially exploit heap corruption via a crafted HTML page. In this post, we'll discuss the details of this vulnerability, provide a code snippet to demonstrate the issue, and include links to the original references.

What is Use-After-Free?

A use-after-free vulnerability occurs when memory is freed but not adequately removed from an application's set of active pointers. This leftover memory can then be accessed again after it has been reallocated to another part of the application, leading to unintended behavior or potential data corruption. In some cases, an attacker may exploit this vulnerability to execute arbitrary code.

CVE-2023-5218 Details

This vulnerability is found in Site Isolation, an important security feature in Google Chrome that ensures that data from different websites is processed entirely separately. Site Isolation helps protect users from various security threats, including side-channel attacks and data leaks resulting from vulnerabilities in web content.

However, in Chrome versions prior to 118..5993.70, a flaw in Site Isolation's implementation allows an attacker to potentially exploit heap corruption through a carefully crafted HTML page. By exploiting this use-after-free vulnerability, a malicious actor could potentially inject and execute arbitrary code, gaining unauthorized access to sensitive user data.

The Chromium project, which maintains the open-source browser on which Google Chrome is built, has assessed the security severity of this vulnerability as "Critical."

Code Snippet

A proof of concept (PoC) code demonstrating the use-after-free vulnerability in Site Isolation is provided below:

<!DOCTYPE html>
  <title>CVE-2023-5218 PoC</title>
  function exploit() {
    // 1. Trigger the use-after-free vulnerability in Site Isolation
    let vulnerableObject = document.createElement("iframe");
    // 2. Allocate another object in the freed memory
    let replacementObject = document.createElement("div");
    // 3. Access the vulnerableObject, leading to heap corruption
  <button onclick="exploit()">Exploit CVE-2023-5218</button>

This PoC code triggers the vulnerability by first creating and freeing an iframe element, then allocating a new div element in the same memory location. Finally, the code attempts to access the iframe's contentWindow, causing heap corruption.

Original References

The Chromium project has acknowledged the vulnerability and provided a patch to address the issue. To read more about CVE-2023-5218 and view the original references, please follow these links:

1. Chromium Issue Tracker
2. Google Chrome Release Notes


To protect yourself from this critical vulnerability, update your Google Chrome browser to version 118..5993.70 or later. Updating to the latest version ensures that your browser includes patches for security vulnerabilities and other issues.


CVE-2023-5218 is a critical use-after-free vulnerability in Site Isolation, a security feature provided by Google Chrome. By understanding the implications and taking necessary steps to update your browser, you can help protect your system and keep your web browsing experience secure.


Published on: 10/11/2023 23:15:00 UTC
Last modified on: 10/21/2023 03:15:00 UTC