CVE-2019-25294: html5_snmp XSS Vulnerability

CVE-2019-25294 Overview

CVE-2019-25294 is a persistent cross-site scripting (XSS) vulnerability affecting html5_snmp version 1.11. The vulnerability allows attackers to inject malicious scripts through the Remark parameter in add_router_operation.php. By crafting a malicious POST request containing a script payload in the Remark field, attackers can execute arbitrary JavaScript code in victim browsers when the affected page is loaded.

Critical Impact

Attackers can inject persistent JavaScript payloads that execute in the context of victim browsers, potentially leading to session hijacking, credential theft, or further attacks against users accessing the affected application.

Affected Products

• html5_snmp version 1.11

Discovery Timeline

• 2026-02-06 - CVE-2019-25294 published to NVD
• 2026-02-06 - Last updated in NVD database

Technical Details for CVE-2019-25294

Vulnerability Analysis

This persistent XSS vulnerability exists due to insufficient input validation and output encoding in the html5_snmp web interface. The add_router_operation.php script accepts user input through the Remark parameter without proper sanitization, allowing attackers to store malicious JavaScript code in the application's database.

When other users access pages that display the stored Remark content, the malicious script executes in their browser context. This type of stored XSS is particularly dangerous because the payload persists on the server and affects all users who view the compromised data, without requiring the attacker to trick victims into clicking specially crafted links.

Root Cause

The root cause is improper input validation (CWE-79: Improper Neutralization of Input During Web Page Generation). The add_router_operation.php script fails to sanitize user-supplied input in the Remark parameter before storing it in the database, and subsequently renders this content without proper output encoding when displaying it to users.

Attack Vector

The attack is network-based and requires an authenticated user with the ability to submit data through the router operation form. The attacker crafts a POST request to add_router_operation.php with a malicious JavaScript payload in the Remark field. Once submitted, this payload is stored persistently and executes whenever any user loads a page that displays the stored remark content.

The attacker can exploit this vulnerability to steal session cookies, redirect users to malicious sites, deface the web interface, or perform actions on behalf of authenticated users. Technical details and a proof-of-concept are available in the Exploit-DB #47587 entry.

Detection Methods for CVE-2019-25294

Indicators of Compromise

• Unusual JavaScript code or HTML tags present in the Remark fields within the database
• Web application logs showing POST requests to add_router_operation.php containing script tags or JavaScript event handlers
• User reports of unexpected browser behavior or redirects when accessing the application

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block common XSS payloads in POST parameters
• Monitor application logs for suspicious input patterns including <script>, javascript:, onerror=, and similar XSS vectors
• Perform regular security audits of stored data fields for injected script content

Monitoring Recommendations

• Enable detailed logging for all form submissions to add_router_operation.php
• Configure intrusion detection systems to alert on XSS payload signatures in HTTP traffic
• Implement Content Security Policy (CSP) headers and monitor for CSP violation reports

How to Mitigate CVE-2019-25294

Immediate Actions Required

• Review and sanitize all existing data in the Remark field for stored malicious content
• Implement strict input validation on the Remark parameter to reject or escape HTML/JavaScript content
• Apply output encoding when displaying user-supplied content to prevent script execution

Patch Information

No official vendor patch has been identified. Organizations using html5_snmp should implement the mitigations described below or consider alternative solutions. For additional security advisory details, refer to the VulnCheck Security Advisory and the GitHub Project Repository.

Workarounds

• Implement server-side input validation to strip or encode HTML special characters from the Remark parameter
• Apply output encoding (HTML entity encoding) when rendering user-supplied content
• Deploy Content Security Policy (CSP) headers to restrict inline script execution
• Consider restricting access to the add_router_operation.php functionality to trusted administrators only

# Example Apache configuration to add Content-Security-Policy header
<IfModule mod_headers.c>
    Header set Content-Security-Policy "default-src 'self'; script-src 'self'"
</IfModule>