CVE-2019-25420: Comodo Dome Firewall XSS Vulnerability

CVE-2019-25420 Overview

CVE-2019-25420 is a reflected cross-site scripting (XSS) vulnerability in Comodo Dome Firewall version 2.7.0. The vulnerability allows attackers to inject malicious scripts by submitting crafted input to the snat endpoint. Attackers can send POST requests with JavaScript payloads in the port or snat_to_ip parameters to execute arbitrary scripts in users' browsers, potentially leading to session hijacking, credential theft, or further attacks against authenticated administrators.

Critical Impact

Attackers can execute arbitrary JavaScript in the context of authenticated Comodo Dome Firewall users, potentially compromising administrative sessions and gaining control over firewall configurations.

Affected Products

• Comodo Dome Firewall 2.7.0

Discovery Timeline

• 2026-02-19 - CVE CVE-2019-25420 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2019-25420

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as reflected cross-site scripting. The flaw exists in how the Comodo Dome Firewall web management interface handles user-supplied input within the SNAT (Source Network Address Translation) configuration endpoint.

When administrators access the snat endpoint, the application fails to properly sanitize or encode user input before reflecting it back in the HTTP response. This lack of input validation allows attackers to craft malicious URLs or forms that, when accessed by an authenticated user, execute arbitrary JavaScript code within the victim's browser session.

The attack requires user interaction, as the victim must be tricked into clicking a malicious link or visiting a compromised page that submits the crafted request on their behalf.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding in the Comodo Dome Firewall web interface. Specifically, the port and snat_to_ip parameters in the snat endpoint are not properly sanitized before being included in the HTTP response. The application directly reflects user-supplied input without encoding special characters such as angle brackets, quotes, and script tags, allowing attackers to inject executable JavaScript code.

Attack Vector

The attack is network-based and requires user interaction. An attacker can exploit this vulnerability by crafting a malicious POST request containing JavaScript payloads within the port or snat_to_ip parameters. The attacker then needs to trick an authenticated administrator into submitting this request, typically through social engineering techniques such as phishing emails containing malicious links or by embedding hidden forms on compromised websites.

When the victim's browser processes the response from the firewall's web interface, the injected JavaScript executes within the security context of the authenticated session. This can allow the attacker to steal session cookies, perform actions on behalf of the administrator, modify firewall rules, or redirect the user to malicious sites.

For technical details on the exploitation method, refer to the Exploit-DB #46408 entry or the VulnCheck Advisory on Comodo Dome.

Detection Methods for CVE-2019-25420

Indicators of Compromise

• Unusual HTTP POST requests to the /snat endpoint containing JavaScript code or HTML tags in the port or snat_to_ip parameters
• Web server logs showing requests with encoded script tags (<script>, %3Cscript%3E) in SNAT-related parameters
• Unexpected session activity or administrative actions following user reports of clicking suspicious links

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing common XSS payloads in POST parameters
• Monitor HTTP access logs for requests to the snat endpoint with suspicious parameter values containing script tags or event handlers
• Deploy browser-based XSS detection tools to identify reflected content in administrative interfaces

Monitoring Recommendations

• Enable verbose logging on the Comodo Dome Firewall web interface to capture all POST request parameters
• Configure SIEM alerts for patterns matching XSS attempts such as <script>, javascript:, or onerror= in HTTP request logs
• Implement network monitoring to detect unusual traffic patterns to the firewall management interface from untrusted sources

How to Mitigate CVE-2019-25420

Immediate Actions Required

• Restrict access to the Comodo Dome Firewall web management interface to trusted internal networks only
• Implement network segmentation to limit exposure of the administrative interface
• Deploy a web application firewall (WAF) in front of the management interface to filter malicious XSS payloads
• Educate administrators about phishing attacks and the risks of clicking untrusted links while authenticated to the firewall

Patch Information

Consult the Comodo Firewall Overview page for information about updated versions and security patches. Users should upgrade to the latest available version of Comodo Dome Firewall that addresses this vulnerability.

Workarounds

• Implement Content Security Policy (CSP) headers at the network level to prevent inline script execution
• Use browser extensions that block JavaScript execution on administrative interfaces when clicking external links
• Access the firewall management interface only from isolated administrative workstations that do not browse external websites

# Example: Restrict access to management interface by IP using iptables
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP