CVE-2024-45962

Executive Summary

CVE-2024-45962 is a Cross-Site Scripting (XSS) vulnerability in October CMS version 3.6.30. An authenticated admin user can upload a PDF file containing malicious JavaScript. When the PDF is accessed via the website, the embedded JavaScript executes in the context of the victim's browser, leading to potential session hijacking, data theft, or arbitrary code execution. The vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation). No official patch has been released at the time of analysis.

Supply Chain & Package Security

October CMS is a PHP-based content management system. The vulnerability lies in the file upload handling mechanism, specifically for PDF files. The core issue is that the application does not sanitize or validate the content of uploaded PDF files for embedded JavaScript. This is a supply chain risk for any organization using October CMS, as an attacker with admin credentials can compromise the integrity of the system by uploading malicious PDFs.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder. Based on the description, a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – The attack is performed over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): High (H) – Requires an authenticated admin account.
• User Interaction (UI): Required (R) – The victim must access the uploaded PDF.
• Scope (S): Changed (C) – The vulnerability can impact resources beyond the vulnerable component.
• Confidentiality (C): High (H) – Potential for data theft.
• Integrity (I): High (H) – Potential for arbitrary code execution.
• Availability (A): Low (L) – Limited impact on availability.

Estimated CVSS Score: 7.1 (High)

Threat Level: High – Exploitation requires admin credentials, but the impact is significant.

Deep Dive & Mechanics

The vulnerability exists in the file upload functionality of October CMS. When an admin uploads a PDF file, the system does not inspect the PDF's internal structure for embedded JavaScript. PDF files can contain JavaScript that executes when the PDF is opened in a browser or PDF viewer. The attack flow is:

1. Authentication: The attacker must have an admin account on the October CMS instance.
2. Upload: The attacker uploads a crafted PDF file containing malicious JavaScript.
3. Access: The victim (e.g., another admin or site visitor) accesses the uploaded PDF via the website.
4. Execution: The browser or PDF viewer executes the embedded JavaScript, leading to XSS.

The JavaScript can perform actions such as stealing session cookies, redirecting to malicious sites, or performing actions on behalf of the victim.

Vulnerable vs. Patched Code

Vulnerable Code (October CMS 3.6.30):

The file upload handler does not sanitize PDF content. The relevant code might look like:

// Vulnerable: No content validation
public function uploadFile($file) {
    $path = $file->store('uploads');
    // No check for embedded JavaScript
    return $path;
}

Patched Code (Hypothetical):

A patch would involve validating the PDF content to ensure no JavaScript is embedded. This could be done using a library like pdftotext or by parsing the PDF structure.

// Patched: Validate PDF content
public function uploadFile($file) {
    $path = $file->store('uploads');
    $pdfContent = file_get_contents($path);
    if (preg_match('/\/JavaScript/i', $pdfContent)) {
        // Reject file
        unlink($path);
        throw new Exception('PDF contains JavaScript');
    }
    return $path;
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Admin credentials for October CMS.
• A tool to craft a PDF with embedded JavaScript (e.g., pdfkit or a hex editor).

Steps:

1. Craft Malicious PDF: Use a tool like pdfkit to create a PDF with embedded JavaScript. Example using Python:

   from pdfkit import from_string
   js_code = """
   <script>
   alert('XSS');
   </script>
   """
   pdf = from_string(js_code, False)
   with open('malicious.pdf', 'wb') as f:
       f.write(pdf)
   

2. Upload PDF: Log in to October CMS admin panel, navigate to file upload, and upload malicious.pdf.

3. Trigger XSS: Access the uploaded PDF via the website URL. The JavaScript will execute.

Blue Team

Detection:

• Monitor file uploads for PDF files with suspicious content.
• Use YARA rules to detect embedded JavaScript in PDFs.
• Enable Content Security Policy (CSP) headers to mitigate XSS.

Prevention:

• Restrict admin account privileges.
• Implement file upload validation to reject PDFs with JavaScript.
• Use a web application firewall (WAF) to block malicious PDF uploads.

Indicators of Compromise (IOCs)

• File Hashes: (Example) malicious.pdf SHA256: a1b2c3d4e5f6...
• Network Traffic: HTTP POST requests to /backend/.../upload with PDF files.
• Logs: Admin user activity logs showing PDF uploads.
• JavaScript Execution: Browser console logs showing unexpected JavaScript execution.

Detection Engineering

YARA Rule

rule October_CMS_PDF_XSS {
    meta:
        description = "Detects PDF files with embedded JavaScript targeting October CMS"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-45962"
    strings:
        $js = "/JavaScript" nocase
        $pdf = "%PDF" nocase
    condition:
        $pdf at 0 and $js
}

Sigma Rule

title: October CMS PDF Upload with Embedded JavaScript
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects upload of PDF files containing JavaScript in October CMS
author: Valters IT
logsource:
    category: file_event
    product: windows
detection:
    selection:
        EventID: 11
        Image|endswith: '\php.exe'
        TargetFilename|endswith: '.pdf'
    condition: selection
falsepositives:
    - Legitimate PDFs with JavaScript (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"October CMS PDF Upload with JavaScript"; flow:to_server,established; content:"POST"; http_method; content:"/backend/"; http_uri; content:".pdf"; file_data; content:"/JavaScript"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Disable PDF upload functionality if not required.
   • Review and restrict admin accounts.
   • Implement a WAF rule to block PDF uploads with JavaScript.

2. Long-term Fix:

   • Apply vendor patch when available.
   • Implement file content validation for all uploads.
   • Use a PDF sanitization library to strip JavaScript.

3. Monitoring:

   • Enable logging for file uploads.
   • Monitor for anomalous admin behavior.

Valters IT
DevSecOps & Cyber Threat Intelligence