In 2024, a serious vulnerability—CVE-2024-21725—was reported widely affecting web applications due to improper email address handling. The flaw? Developers failed to correctly escape special characters in email addresses, resulting in Cross-Site Scripting (XSS) vulnerabilities across admin panels, user directories, and notification features. Let’s break down what happened, how it affects your application, and see an exploit in action.

What is CVE-2024-21725?

CVE-2024-21725 refers to a class of vulnerabilities where software using user email input in the UI did not sanitize or “escape” special characters. This oversight allows attackers to inject malicious JavaScript via crafted email addresses, which then gets executed in other users’ browsers—classic XSS.

How the Vulnerability Happens

Consider a signup process that saves the email without escaping it, and later displays it in the admin dashboard. If nothing checks for special HTML characters, an attacker can register with:

attacker@example.com"><script>alert('XSS')</script>

If your application renders this directly

<td>attacker@example.com"><script>alert('XSS')</script></td>

The browser interprets this as a script tag and *runs the JavaScript code*.

Insecure PHP snippet

// admin_panel.php
echo "<td>" . $_POST['email'] . "</td>";

When a user registered with the “evil” email above, any admin viewing the page would trigger the alert and expose themselves to further attacks.

Secure (patched) version

// admin_panel.php
echo "<td>" . htmlspecialchars($_POST['email'], ENT_QUOTES, 'UTF-8') . "</td>";

Email notifications that included sender emails in HTML bodies.

This means that attackers could compromise higher-privileged accounts, steal session cookies, or spread more malware—all by registering or updating an email address.

Here’s a full Proof-of-Concept HTML file simulating a vulnerable admin dashboard

<!-- vulnerable_dashboard.html -->
<html>
<head><title>Vulnerable Emails</title></head>
<body>
  <table>
    <tr>
      <td>alice@example.com</td>
    </tr>
    <tr>
      <td>attacker@example.com"><script>alert('XSS from CVE-2024-21725')</script></td>
    </tr>
  </table>
</body>
</html>

Open this in your browser, and an attacker’s script would execute.

In PHP

echo htmlspecialchars($email, ENT_QUOTES, 'UTF-8');

In JavaScript (React)

<td>{email}</td> // Safe, because React escapes output automatically.

In Python (Django)

# Safe in Django templates: {{ email }} 
# If you must output raw HTML:
from django.utils.html import escape
safe_email = escape(email)

References

- CVE-2024-21725 - Official NVD Details
- OWASP XSS Prevention Cheat Sheet
- Stack Overflow: How to Escape Output

Final Thoughts

CVE-2024-21725 is a reminder: *never trust user input—even email addresses!* Always escape output to prevent attackers from injecting code in your application. Run code scanning tools, use safe frameworks, and double-check any time user data is rendered in HTML.

Do you have vulnerable code? Patch it right away, and stay safe from sneaky email-based XSS!

Timeline

Published on: 02/29/2024 01:44:03 UTC
Last modified on: 10/27/2024 02:35:00 UTC