Firefox for iOS, URL Spoofing Vulnerability, CVE-2025-23109 (Medium)

How the CVE Works:

CVE-2025-23109 exploits Firefox for iOS (versions below 134) by allowing attackers to craft excessively long hostnames in URLs. This obscures the true destination, enabling address bar spoofing. The browser fails to truncate or validate these lengthy hostnames, making phishing attacks easier as users may mistake a malicious site for a legitimate one due to visual truncation in the UI.

DailyCVE Form:

Platform: Firefox for iOS
Version: < 134
Vulnerability: URL hostname spoofing
Severity: Medium
Date: 01/10/2025

What Undercode Say:

Exploitation:

1. Craft a URL with an abnormally long hostname (e.g., `https://verylongsubdomain

   fake.example.com`).</li>
   <li>The rendered address bar truncates the display, hiding the true domain (<code>fake.example.com</code>).</li>
   <li>Victims perceive the truncated URL as legitimate (e.g., <code>verylongsubdomain[bash].example.com</code>).</li>
   </ol>
   
   <h2 style="color: blue;">Detection:</h2>
   
   [bash]
   Check Firefox iOS version:
   grep -i "firefox" /Applications/Firefox.app/Info.plist | grep -i "CFBundleVersion"
   

   Mitigation:

   1. Update Firefox for iOS to v134+.

   1. Implement client-side validation to reject URLs exceeding 255 characters:

      if (url.hostname.length > 255) {
      alert("Invalid URL: Hostname too long");
      }
      

   3. Enable phishing protections in Firefox settings.

   Analytics:

   • Attack Vector: Network-based (phishing).
   • CVSS 4.0 Score: 5.4 (Medium) – AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.
   • Patch Reference: Mozilla Security Advisory

     .</li>
     </ul>
     
     <h2 style="color: blue;">Tools:</h2>
     
     <ul>
     <li>URL Spoof Tester:
     [bash]
     def is_spoofable(url):
     return len(url.split("//")[bash].split("/")[bash]) > 255
     

   • WAF Rule: Block HTTP requests with hostnames > 255 chars.

   User Protection:

   • Train users to inspect full URLs before clicking.
   • Use browser extensions that flag suspicious hostnames.

   References:

   Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-23109
   Extra Source Hub:
   Undercode

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