CVE-2019-25421: Comodo Dome Firewall XSS Vulnerability

CVE-2019-25421 Overview

Comodo Dome Firewall 2.7.0 contains multiple cross-site scripting (XSS) vulnerabilities that allow attackers to inject malicious scripts through the policyfw endpoint. Attackers can submit POST requests with JavaScript payloads in the mac, target, and remark parameters to execute arbitrary code in administrator browsers or store persistent scripts in the application.

Critical Impact

Successful exploitation enables attackers to execute arbitrary JavaScript in the context of an authenticated administrator's browser session, potentially leading to session hijacking, credential theft, or unauthorized firewall configuration changes.

Affected Products

• Comodo Dome Firewall 2.7.0

Discovery Timeline

• 2026-02-19 - CVE CVE-2019-25421 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2019-25421

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The Comodo Dome Firewall web management interface fails to properly sanitize user-supplied input before rendering it in the browser context.

The vulnerable policyfw endpoint accepts POST requests containing user-controlled data in the mac, target, and remark parameters. When this data is processed and displayed back to users without proper encoding or escaping, any embedded JavaScript code executes within the victim's browser session. This is particularly dangerous in a firewall management context, where administrators typically have elevated privileges to modify security policies.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and output encoding within the Comodo Dome Firewall web application. The application fails to implement proper XSS prevention mechanisms such as HTML entity encoding, Content Security Policy headers, or input sanitization filters on the affected parameters. When user-supplied data containing script tags or JavaScript event handlers is submitted to the policyfw endpoint, the application stores or reflects this content without neutralizing potentially malicious characters.

Attack Vector

This is a network-based attack that requires user interaction. An attacker can craft a malicious request containing JavaScript payloads and either:

1. Reflected XSS: Trick an administrator into clicking a specially crafted link that submits the malicious payload to the vulnerable endpoint
2. Stored XSS: Submit malicious content that gets stored in the application database and executed whenever other users view the affected page

The attack targets the firewall's web management interface, making administrators the primary victims. Once JavaScript executes in the administrator's browser, the attacker can perform actions such as stealing session cookies, modifying firewall rules, creating backdoor accounts, or pivoting to attack internal network resources.

The vulnerability affects three parameters in POST requests to the policyfw endpoint:

• mac - MAC address field
• target - Target specification field
• remark - Comment/remark field

Each of these parameters accepts arbitrary input that is not properly sanitized before being rendered in the administrative interface.

Detection Methods for CVE-2019-25421

Indicators of Compromise

• Unusual JavaScript content in firewall policy database fields (mac, target, remark)
• Web server logs showing POST requests to /policyfw containing <script> tags or JavaScript event handlers
• Unexpected administrator session activity or policy modifications
• Browser-based requests originating from administrator sessions to external domains

Detection Strategies

• Monitor HTTP POST requests to the policyfw endpoint for script injection patterns such as <script>, javascript:, onerror=, onload=, and similar XSS payloads
• Implement Web Application Firewall (WAF) rules to detect and block XSS attack patterns targeting the Comodo Dome Firewall management interface
• Review firewall policy configurations for suspicious entries containing encoded or obfuscated JavaScript content
• Enable verbose logging on the firewall management interface to capture all administrative actions

Monitoring Recommendations

• Configure SIEM alerts for XSS attack signatures targeting the Comodo Dome Firewall web interface
• Implement network-level monitoring for exfiltration attempts from administrator workstations
• Regularly audit stored policy data for signs of injection attacks
• Monitor for unauthorized changes to firewall rules that may indicate post-exploitation activity

How to Mitigate CVE-2019-25421

Immediate Actions Required

• Restrict access to the Comodo Dome Firewall management interface to trusted networks and IP addresses only
• Implement a Web Application Firewall (WAF) in front of the management interface to filter XSS payloads
• Enable browser-based XSS protection headers and Content Security Policy where possible
• Audit existing firewall policies for malicious content and remove any suspicious entries

Patch Information

No vendor patch information is currently available for this vulnerability. Organizations should consult the Comodo Firewall product page for updates and security advisories. Additional technical details are available in the VulnCheck Advisory and Exploit-DB #46408.

Workarounds

• Restrict management interface access to localhost or a dedicated management VLAN with strict access controls
• Implement network segmentation to isolate the firewall management interface from general user traffic
• Use a reverse proxy with input validation capabilities to filter requests before they reach the firewall interface
• Train administrators to avoid clicking links from untrusted sources while logged into the management interface
• Consider disabling the web management interface entirely and using CLI-based administration if possible

# Configuration example - Network ACL to restrict management access
# Restrict firewall management interface to trusted admin subnet
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP