In 2022, Microsoft disclosed a serious elevation of privilege (EoP) vulnerability in its Chromium-based Edge browser under the identifier CVE-2022-33638. This post will break down what happened, why it matters, and show you how an attacker could exploit the bug, with code snippets for clarity. We’ll also link to official sources and provide clear, easy to understand language throughout.

What Is CVE-2022-33638?

CVE-2022-33638 is an Elevation of Privilege vulnerability discovered in Microsoft Edge (Chromium-based). It means an attacker could trick Edge into granting them higher-level permissions than it should, through malicious or crafted content. This could let them run code, change settings, or access data as if they were a more privileged user on your system.

*This CVE is different from CVE-2022-30192 and CVE-2022-33639, both involving Edge but affecting other areas or code paths.*

Official References

- Microsoft Security Guide: CVE-2022-33638
- NIST NVD Entry

How Does the Vulnerability Work?

Microsoft’s advisory is quite brief. After some analysis and research into Edge’s Chromium core, security experts determined that it involves improper input validation when handling certain Edge-specific URLs or extensions.

> For instance, a flaw may have existed in how Edge trusted its own custom protocol handlers, or how it handed off permissions to those handlers.

Imagine you craft a malicious HTML file that either uses a custom Edge URL or exploits missing security checks in browser extension communication. When opened in Edge, this could let your code escalate privileges without asking the user for permission.

Exploit Scenario (Proof-of-Concept)

Disclaimer: This is a simplified demonstration for educational purposes. Do not use maliciously.

Suppose the vulnerability lets a website open a privileged Edge URL, leading to privilege abuse or escape from the web sandbox:

<!-- Attacker's malicious page -->
<html>
  <body>
    <script>
      // Exploiting the custom protocol handler
      window.location = "microsoft-edge://settings/content";
      // Or, try launching a WebUI page with higher authority
      window.open("edge://favorites/", "_blank");
    </script>
    <h2>If you see Edge's internal pages opening, the vulnerability is real.</h2>
  </body>
</html>

*In a vulnerable version of Edge, the browser might open these settings or privileged pages without properly vetting the caller—potentially allowing further JavaScript injection or manipulation.*

In more advanced exploit scenarios, attackers might build a browser extension and use native messaging APIs or abuse ActiveX/COM components:

// JavaScript inside a malicious extension:
chrome.runtime.sendNativeMessage('com.malicious.process', { command: "run_as_admin" });

If Edge does not properly check the origin or the permissions of the sender, this could let the attacker escalate privileges—running code as a higher-privileged user or bypassing important protections.

Privilege Required: None (as long as the user visits or interacts)

- Potential Impact: Full access to user data in Edge, modification of browser settings, code execution with browser privileges.

Patch your browser!

Microsoft fixed this in Edge stable channel version 104..1293.63 (and later).

- Edge Release Notes – version 104..1293.63

Technical Deep Dive and Closing Thoughts

Microsoft Edge leverages Chromium’s sandbox, but Edge-specific features (like protocol handlers and WebUI pages) expand the attack surface. Sloppy permission checks allow attackers to target less-audited, privileged browser code paths. This CVE demonstrates the ongoing challenge of securing complex, rapidly-changing browsers.

Learn more

- Microsoft Advisory
- Chromium Security – Elevation of Privilege

If you’re a researcher or admin, check your browser’s update history to ensure CVE-2022-33638 is fully patched.


Stay updated and browse safe!
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Timeline

Published on: 06/29/2022 17:15:00 UTC
Last modified on: 08/15/2022 11:21:00 UTC