In May 2022, Microsoft published details about a security flaw in their Chromium-based Edge browser, registered as CVE-2022-22021. This critical vulnerability enables remote attackers to execute code on the victim’s system, potentially taking over a user’s machine just by luring them to a malicious website. In this post, we’ll break down how this vulnerability works, demonstrate it with simplified code, and walk you through its real-world impact. We’ll also link to trusted resources for deeper research.

> Disclaimer:  
> This post is for educational purposes only. Do not exploit vulnerabilities on systems you do not own or have permission to test.

Severity: Critical (CVSS 8.8-9.6 depending on vector)

- Official Advisory: Microsoft Vulnerability Guide – CVE-2022-22021

How does it happen?

CVE-2022-22021 is caused by improper memory operations when Edge is processing specific web content, like a carefully crafted HTML or JavaScript payload. An attacker can use a malicious website to trigger the flaw, gaining the ability to run code–essentially turning a browser session into a doorway to the whole system.

Technical Details

The core issue lies in the way that Edge handles JavaScript objects or media files. By creating specially structured content, like a heap spray or a use-after-free condition, an attacker can corrupt the browser's memory.

Here's a simplified example to help you understand the idea (note: this code is an illustrative snippet, not a live exploit):

// This is a conceptual example and does NOT exploit the real CVE-2022-22021
// It demonstrates how a use-after-free could be triggered in Chromium-based browsers.

// Step 1: Create an object
let victimObject = new ArrayBuffer(x100);

// Step 2: Create a function that will trigger garbage collection
function triggerGC() {
    for (let i = ; i < 10000; i++) {
        let temp = new ArrayBuffer(x100);
    }
}

// Step 3: Nullify the reference and force garbage collection
victimObject = null;
triggerGC();

// Step 4: Attempt to access freed memory (in reality, this could lead to code execution)
console.log(victimObject); // In Edge's vulnerable version, this might point to freed memory

Real attackers use more sophisticated versions of this approach, chaining several vulnerabilities together (memory corruption, type confusion, etc.) to gain *arbitrary code execution*.

Malicious Web Page:

The attacker sets up a website with crafted JavaScript/HTML that exploits the Edge bug.

Code runs on victim’s system, potentially installing malware or stealing data.

Example exploit chain:  
- A proof-of-concept could execute arbitrary commands on Windows using PowerShell, after gaining initial code execution through the browser flaw.

Sample Proof of Concept (POC) Steps

While Microsoft has understandably withheld full details and POC code to prevent abuse, security researchers often create safe payloads like calculators as a demonstration.

For example

// After leveraging the memory corruption, attacker achieves JS shell
let shellcode = "...binary shellcode here...";
let rwx = allocateRWXMemory(shellcode);
callShellcode(rwx); // This would run arbitrary native code

On Windows, shellcode could launch the calculator via

calc.exe

Update Edge:

The safest move is to update Microsoft Edge regularly. Microsoft patched this vulnerability in Edge version 101..121.53 and later.

Auto-Updates:

Chromium-based browsers (like Edge) auto-update. Still, verify your browser is up-to-date by going to Settings > About Microsoft Edge.

Disable JavaScript:

As a temporary block, disabling JavaScript mitigates many exploitation paths (but breaks site functionality).

References and Further Reading

- MSRC Advisory for CVE-2022-22021
- NIST NVD Entry
- Chromium Security Releases
- How Edge Auto-Update Works
- Project Zero: Exploiting Browser Memory Corruptions

Conclusion

CVE-2022-22021 is a critical Microsoft Edge (Chromium-based) flaw that shows how just browsing the web can expose your entire computer to risk. While technical exploitation requires skill, criminals can weaponize such flaws quickly. The best defense is keeping browsers up-to-date and staying vigilant online.

If you’re interested in browser security, read Microsoft’s and Chromium’s official advisories, and always responsibly disclose new bugs.

> Stay safe, keep your software current, and never run unknown code.


*(This exclusive guide is written in plain language to demystify a complex security threat. Please share for educational purposes only!)*

Timeline

Published on: 06/15/2022 22:15:00 UTC
Last modified on: 08/19/2022 12:49:00 UTC