CVE-2019-25428: Comodo Dome Firewall XSS Vulnerability

CVE-2019-25428 Overview

CVE-2019-25428 is a reflected Cross-Site Scripting (XSS) vulnerability affecting Comodo Dome Firewall version 2.7.0. The vulnerability exists in the openvpn_users endpoint, where multiple POST parameters fail to properly sanitize user input before reflecting it back in the HTTP response. This allows attackers to inject malicious JavaScript code that executes in the context of an authenticated user's browser session.

The vulnerable parameters include username, remotenets, explicitroutes, static_ip, custom_dns, and custom_domain. When an attacker crafts a malicious POST request containing script payloads in any of these parameters, the server reflects the unvalidated input directly into the response, enabling arbitrary JavaScript execution.

Critical Impact

Attackers can leverage this XSS vulnerability to steal session cookies, hijack administrator sessions, perform unauthorized actions on the firewall, or redirect users to malicious sites, potentially compromising the entire network perimeter security.

Affected Products

• Comodo Dome Firewall 2.7.0
• Comodo Dome Firewall (versions prior to security patch)
• OpenVPN user management interface within Comodo Dome Firewall

Discovery Timeline

• 2026-02-19 - CVE-2019-25428 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2019-25428

Vulnerability Analysis

This reflected XSS vulnerability (CWE-79) stems from insufficient input validation in the openvpn_users endpoint of the Comodo Dome Firewall web interface. The vulnerability requires user interaction, as victims must be tricked into submitting or clicking on a malicious link that triggers the crafted POST request.

The attack exploits the trust relationship between the user's browser and the firewall's web management interface. Since the firewall is a critical network security appliance, successful exploitation could have severe consequences including unauthorized configuration changes, credential theft, and persistent access through injected malicious scripts.

The network-based attack vector means exploitation can occur remotely, though the requirement for user interaction reduces the immediate exploitability. No authentication is required to craft the malicious request, but the attack's effectiveness depends on targeting authenticated administrators.

Root Cause

The root cause of this vulnerability is improper input validation and output encoding in the openvpn_users endpoint. When POST parameters are submitted to configure OpenVPN users, the application fails to sanitize special characters and HTML entities before including them in the server response. This lack of proper output encoding allows script tags and JavaScript event handlers to be interpreted and executed by the victim's browser rather than being rendered as harmless text.

Attack Vector

The attack leverages a network-based vector targeting the Comodo Dome Firewall web management interface. An attacker would craft a malicious HTML form or link that, when accessed by an authenticated administrator, submits a POST request to the openvpn_users endpoint containing JavaScript payloads in vulnerable parameters.

The attacker might deliver this payload through phishing emails, compromised websites, or social engineering tactics. When the victim interacts with the malicious content, their browser executes the injected JavaScript in the context of their authenticated session with the firewall management interface. This grants the attacker the ability to perform any action the administrator could perform, including modifying firewall rules, creating backdoor accounts, or exfiltrating sensitive configuration data.

For technical details and proof-of-concept information, refer to Exploit-DB #46408 and the VulnCheck Advisory on Comodo.

Detection Methods for CVE-2019-25428

Indicators of Compromise

• Unusual POST requests to the openvpn_users endpoint containing script tags or JavaScript event handlers
• Web server logs showing encoded or obfuscated script payloads in URL parameters or POST bodies
• Unexpected JavaScript execution or browser console errors on the firewall management interface
• Session cookie theft attempts or unauthorized session activity from unexpected IP addresses

Detection Strategies

• Deploy web application firewall (WAF) rules to detect and block XSS payloads in POST parameters targeting the openvpn_users endpoint
• Implement content security policy (CSP) headers to prevent inline script execution and mitigate XSS impact
• Monitor web server access logs for requests containing suspicious patterns like <script>, javascript:, or common XSS vectors
• Enable browser-based XSS auditing and configure security headers including X-XSS-Protection

Monitoring Recommendations

• Configure SIEM alerts for POST requests to firewall management interfaces containing encoded HTML entities or script patterns
• Monitor for anomalous administrative session behavior that may indicate session hijacking
• Track failed and successful authentication attempts to the firewall management interface for signs of unauthorized access
• Review firewall configuration change logs for unexpected modifications that may have been performed via XSS exploitation

How to Mitigate CVE-2019-25428

Immediate Actions Required

• Restrict access to the Comodo Dome Firewall web management interface to trusted IP addresses and networks only
• Implement network segmentation to isolate the firewall management interface from general user networks
• Deploy a web application firewall (WAF) in front of the management interface to filter XSS payloads
• Educate administrators about phishing attacks and the risks of clicking untrusted links while authenticated to security appliances

Patch Information

Organizations should consult the Comodo Firewall Overview for the latest firmware and patch availability. Contact Comodo support to obtain security updates that address this XSS vulnerability. Ensure all Comodo Dome Firewall appliances are running the latest available firmware version with security patches applied.

Review the VulnCheck Advisory on Comodo for additional guidance on remediation.

Workarounds

• Limit administrative access to the firewall management interface to a dedicated management VLAN or jump host
• Implement strict Content-Security-Policy headers at the network level using a reverse proxy if direct patching is not immediately available
• Use separate browser profiles or dedicated machines for firewall administration that are not used for general web browsing
• Enable multi-factor authentication for firewall administrative access to reduce the impact of session hijacking

# Configuration example - Restrict management interface access via iptables
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Alternatively, configure access restrictions in firewall management settings
# Consult Comodo documentation for built-in access control configuration