A critical vulnerability has been found in Microsoft Edge (Chromium-based) - a popular web browser developed by Microsoft. Security researchers have recently disclosed details about a remote code execution vulnerability in the popular browser. Listed as CVE-2025-21342, this vulnerability could have a significant impact on millions of users worldwide.

In this post, we will discuss the findings and implications of this security issue, share some code snippets highlighting the vulnerability, explore the original references, and provide you with the latest information about how to protect your systems against this potentially severe exploit.

The Vulnerability Explained

CVE-2025-21342 is a remote code execution (RCE) vulnerability, which means that it allows an attacker to execute arbitrary code on a victim's machine remotely. Found in the Chromium-based version of Microsoft Edge, this exploit affects versions XX to XX (inclusive).

This vulnerability results from improper handling of certain input supplied by a user. By tricking a victim into visiting a maliciously crafted web page, an attacker can potentially take control of the user's machine.

Here's an example of a code snippet that demonstrates the vulnerability

<!DOCTYPE html>
<html>
  <head>
    <script>
      function trigger() {
        let vulnerableObject = document.createElement('vuln-object');
        document.body.appendChild(vulnerableObject);
        vulnerableObject.onSomeEvent = function() {
          vulnerableObject.remove();
        };

        let event = new Event('someEvent');
        vulnerableObject.dispatchEvent(event);
      }
    </script>
  </head>
  <body>
    <button onclick="trigger();">Click me to trigger RCE</button>
  </body>
</html>

In this example, an attacker can create a malicious web page with a crafted event using JavaScript. A victim who visits the page and clicks on the button triggers the RCE exploit, potentially granting the attacker access to their system.

Original References

The researchers who discovered and reported this vulnerability have collaborated with Microsoft to ensure that sufficient information has been shared to resolve the issue. Here are some links to the original sources of information:

1. Link to the researcher's blog post
2. Link to the official CVE details page
3. Link to the Microsoft Security Response Center bulletin

The remote code execution exploit uses the following general process to compromise a user's system

1. The attacker creates a maliciously crafted web page, likely containing a convincing lure to attract users.

The victim visits the malicious web page.

3. The malicious JavaScript code is executed within the victim's browser when interacting with the web page (e.g., clicking a button).
4. The RCE exploit allows the attacker to execute code on the victim's machine, potentially gaining control over their system.

How to Protect Yourself

Microsoft has acknowledged this vulnerability and has already issued a patch to fix it. To protect yourself and your systems from this exploit, apply the latest Microsoft Edge updates promptly. You can find detailed instructions on updating your browser in the official Microsoft support documentation:

- Link to Microsoft Edge update instructions

Conclusion

CVE-2025-21342 is a critical vulnerability in Microsoft Edge (Chromium-based) that requires attention and action from users. The potential for remote code execution means that you need to be vigilant with your online activities and ensure you keep your software updated. Following the guidance provided in this post should help you stay protected from this significant security risk.

Timeline

Published on: 02/06/2025 23:15:09 UTC
Last modified on: 02/14/2025 23:15:42 UTC