CVE-2026-30919: facileManager fmDNS Stored XSS Vulnerability

CVE-2026-30919 Overview

CVE-2026-30919 is a stored Cross-Site Scripting (XSS) vulnerability affecting facileManager, a modular suite of web applications designed for system administrators. Prior to version 6.0.4, the fmDNS module fails to properly sanitize user-supplied data before including it in subsequent HTTP responses, enabling persistent XSS attacks. This type of vulnerability, also known as second-order XSS, allows attackers to inject malicious scripts that execute in the browsers of other users viewing the affected content.

Critical Impact
Authenticated attackers can inject persistent malicious scripts into the fmDNS module, potentially compromising other users' sessions, stealing credentials, or performing unauthorized actions on behalf of victims.

Affected Products

facileManager versions prior to 6.0.4
facileManager fmDNS module (all versions prior to 6.0.4)

Discovery Timeline

2026-03-10 - CVE-2026-30919 published to NVD
2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-30919

Vulnerability Analysis

This stored XSS vulnerability exists in the fmDNS module of facileManager due to insufficient input validation and output encoding. When the application receives data from users, it stores this data without proper sanitization and later renders it in HTTP responses without adequate escaping. This allows malicious JavaScript code to be permanently stored on the server and executed whenever other users access the affected pages.

The vulnerability requires low-privileged authenticated access to exploit, making it accessible to any user with basic permissions in the facileManager system. However, exploitation requires user interaction—a victim must view the page containing the injected payload. Successful exploitation can lead to high confidentiality and integrity impacts, including session hijacking, credential theft, and unauthorized administrative actions.

Root Cause

The root cause of this vulnerability is improper input validation and missing output encoding in the fmDNS module (CWE-79: Improper Neutralization of Input During Web Page Generation). The application accepts user-supplied data without sanitizing potentially dangerous characters and scripts, then reflects this unsanitized content back to users in subsequent page loads. This violates the fundamental security principle of treating all user input as untrusted.

Attack Vector

The attack is network-based and requires the attacker to have low-level authentication to the facileManager application. The attacker injects malicious JavaScript payloads into input fields processed by the fmDNS module. These payloads are stored in the application's database and subsequently rendered to other users viewing the affected content.

When a victim user accesses the page containing the stored payload, the malicious script executes in their browser context. This can enable session token theft, keylogging, phishing attacks, or automated actions performed on behalf of the victim. Since the payload persists on the server, it affects all users who view the compromised content until the malicious data is removed or the system is patched.

Detection Methods for CVE-2026-30919

Indicators of Compromise

Unusual JavaScript or HTML tags stored in fmDNS module database fields
Unexpected script execution or browser behavior when accessing fmDNS module pages
Web application firewall (WAF) logs showing XSS payload patterns in POST requests
User reports of unexpected pop-ups, redirects, or credential prompts within facileManager

Detection Strategies

Implement web application firewall rules to detect and block common XSS payload patterns targeting the fmDNS module
Enable detailed access logging for facileManager and monitor for suspicious input containing script tags or event handlers
Deploy Content Security Policy (CSP) headers with strict directives to detect violation attempts
Conduct regular database audits to identify stored content containing suspicious JavaScript or HTML elements

Monitoring Recommendations

Monitor web server logs for POST requests to fmDNS module endpoints containing potential XSS payloads
Set up alerts for CSP violation reports that may indicate attempted or successful XSS exploitation
Implement user behavior analytics to detect anomalous actions that could result from session hijacking
Review browser console errors and network traffic for unexpected script sources or API calls

How to Mitigate CVE-2026-30919

Immediate Actions Required

Upgrade facileManager to version 6.0.4 or later immediately
Review fmDNS module database entries for any stored malicious content and sanitize affected records
Invalidate all active user sessions to prevent exploitation of any compromised session tokens
Implement Content Security Policy headers with strict script-src directives as an additional defense layer

Patch Information

The vulnerability has been addressed in facileManager version 6.0.4. Organizations should upgrade to this version or later to remediate the vulnerability. For detailed information about the fix, refer to the GitHub Security Advisory.

Workarounds

Restrict access to the fmDNS module to only trusted administrative users until patching is complete
Deploy a web application firewall with XSS detection rules in front of the facileManager application
Implement strict Content Security Policy headers to prevent inline script execution
Consider disabling the fmDNS module temporarily if it is not critical to operations

bash

# Example CSP header configuration for Apache
# Add to .htaccess or Apache configuration
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"