CVE-2026-27176 Overview
MajorDoMo (aka Major Domestic Module), a popular open-source home automation platform, contains a reflected cross-site scripting (XSS) vulnerability in command.php. The $qry parameter is rendered directly into the HTML page without sanitization via htmlspecialchars(), both in an input field value attribute and in a paragraph element. An attacker can inject arbitrary JavaScript by crafting a URL with malicious content in the qry parameter.
Critical Impact
Attackers can execute arbitrary JavaScript in the context of authenticated user sessions, potentially leading to session hijacking, credential theft, or unauthorized actions within the home automation system.
Affected Products
- MajorDoMo (Major Domestic Module) - command.php component
- Versions prior to the security patch referenced in GitHub Pull Request #1177
Discovery Timeline
- 2026-02-18 - CVE-2026-27176 published to NVD
- 2026-02-19 - Last updated in NVD database
Technical Details for CVE-2026-27176
Vulnerability Analysis
This reflected XSS vulnerability exists due to insufficient input validation in the command.php script within MajorDoMo. The application fails to properly sanitize user-supplied input from the $qry parameter before rendering it in the HTML response. The vulnerable code outputs the parameter value in two locations: within an input field's value attribute and within a paragraph element, neither of which applies proper HTML entity encoding using htmlspecialchars() or equivalent sanitization functions.
Reflected XSS vulnerabilities of this nature require user interaction, as the victim must click on a malicious link crafted by the attacker. Once clicked, the injected JavaScript executes within the victim's browser session with full access to the application's DOM and cookies.
Root Cause
The root cause is improper input sanitization (CWE-79: Improper Neutralization of Input During Web Page Generation). The $qry parameter is directly echoed into the HTML output without applying proper encoding, allowing an attacker to break out of the HTML context and inject malicious script tags or event handlers.
Attack Vector
The attack vector is network-based, requiring an attacker to craft a malicious URL containing JavaScript payload in the qry parameter. When an authenticated user clicks this link, the malicious script executes in their browser within the context of the MajorDoMo application. This could allow attackers to:
- Steal session cookies and authentication tokens
- Perform actions on behalf of the authenticated user
- Redirect users to phishing pages
- Modify home automation settings or device configurations
The vulnerability is exploited by injecting JavaScript into the qry parameter. For example, an attacker might craft a URL containing script tags or event handlers that execute when the page renders. The malicious payload could close the existing HTML attribute context, inject a script element, and execute arbitrary code. Technical details and proof-of-concept information can be found in the Chocapikk Blog Post and the VulnCheck Advisory.
Detection Methods for CVE-2026-27176
Indicators of Compromise
- Suspicious HTTP requests to command.php containing encoded script tags or JavaScript event handlers in the qry parameter
- URL-encoded payloads such as %3Cscript%3E, %22onmouseover%3D, or similar injection patterns in request logs
- Unusual outbound connections from client browsers after visiting MajorDoMo pages
Detection Strategies
- Implement web application firewall (WAF) rules to detect and block XSS payloads in request parameters
- Monitor HTTP access logs for suspicious patterns in the qry parameter, including HTML tags and JavaScript event handlers
- Deploy browser-based XSS detection through Content Security Policy (CSP) violation reporting
- Use intrusion detection systems (IDS) with signatures for common XSS attack patterns
Monitoring Recommendations
- Enable detailed logging for all requests to command.php and review for anomalous patterns
- Configure alerting for requests containing potential XSS payloads such as <script>, javascript:, or HTML event attributes
- Monitor for CSP violations which may indicate attempted XSS exploitation
- Review authentication logs for any suspicious session activity following detected XSS attempts
How to Mitigate CVE-2026-27176
Immediate Actions Required
- Apply the security patch from GitHub Pull Request #1177 immediately
- Implement Content Security Policy (CSP) headers to restrict inline script execution
- Review and audit all user input handling in the MajorDoMo codebase for similar vulnerabilities
- Educate users about the risks of clicking untrusted links
Patch Information
A security fix is available via GitHub Pull Request #1177. The patch adds proper input sanitization using htmlspecialchars() to encode special characters before rendering user input in HTML contexts. Organizations should update to the patched version as soon as possible. Additional technical details are available in the VulnCheck Advisory.
Workarounds
- Implement a web application firewall (WAF) rule to filter requests containing potential XSS payloads in the qry parameter
- Restrict access to command.php to trusted networks or authenticated users only until the patch can be applied
- Add Content-Security-Policy headers at the web server level to mitigate the impact of any successful XSS attacks
# Example Apache configuration for CSP header
<IfModule mod_headers.c>
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';"
</IfModule>
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
