CVE-2020-36905: FIBARO Home Center RCE Vulnerability

CVE-2020-36905 Overview

CVE-2020-36905 is a Remote File Inclusion (RFI) vulnerability affecting FIBARO System Home Center version 5.021. The vulnerability exists in an undocumented proxy API endpoint that fails to properly validate the url GET parameter. This allows remote attackers to include arbitrary client-side scripts, enabling cross-site scripting (XSS) attacks that can hijack user sessions or manipulate page content within the smart home management interface.

Critical Impact
Attackers can inject malicious JavaScript through the vulnerable proxy API, potentially compromising user sessions and gaining unauthorized control over smart home devices managed by the FIBARO Home Center.

Affected Products

FIBARO System Home Center version 5.021
FIBARO Home Center smart home controllers running vulnerable firmware

Discovery Timeline

2026-01-06 - CVE CVE-2020-36905 published to NVD
2026-01-08 - Last updated in NVD database

Technical Details for CVE-2020-36905

Vulnerability Analysis

This vulnerability is classified under CWE-829 (Inclusion of Functionality from Untrusted Control Sphere). The FIBARO System Home Center exposes an undocumented proxy API that is designed to fetch and display content from external URLs. However, the implementation lacks proper input validation and sanitization on the url parameter, allowing attackers to inject malicious content that gets rendered in the context of the victim's browser session.

The network-accessible attack vector means that any attacker with network access to the Home Center device can exploit this vulnerability. Since FIBARO Home Centers are smart home controllers that manage connected IoT devices such as lights, locks, sensors, and thermostats, successful exploitation could have significant implications for physical security and privacy.

Root Cause

The root cause of this vulnerability lies in the insufficient validation of user-supplied input in the proxy API endpoint. The url GET parameter is processed without proper sanitization, allowing attackers to supply malicious URLs that include JavaScript code. When the proxy fetches and returns this content, the malicious scripts execute in the context of the authenticated user's session.

The undocumented nature of this API suggests it may have been included for debugging or development purposes and was inadvertently left accessible in production firmware, compounding the security risk.

Attack Vector

The attack exploits the network-accessible proxy API by crafting a malicious URL that includes JavaScript payloads. When a victim user is tricked into clicking a crafted link or when the malicious URL is embedded in the Home Center interface, the proxy fetches the attacker-controlled content and renders it within the trusted domain context.

This enables several attack scenarios including session token theft, phishing attacks within the Home Center interface, modification of smart home configurations, and potential takeover of connected IoT devices. The attack requires user interaction (clicking a malicious link), but no authentication is required to craft and deliver the exploit.

Technical details and proof-of-concept information are available through the ZeroScience Vulnerability Advisory ZSL-2020-5563 and Exploit-DB #48240.

Detection Methods for CVE-2020-36905

Indicators of Compromise

Unusual HTTP requests to the Home Center proxy API endpoint containing external URLs
JavaScript injection patterns in URL parameters targeting the Home Center web interface
Unexpected outbound connections from the Home Center device to unknown external hosts
Session anomalies or unauthorized configuration changes in the Home Center logs

Detection Strategies

Monitor network traffic for requests to the proxy API endpoint with suspicious URL parameters
Implement web application firewall (WAF) rules to detect and block URL injection attempts
Review Home Center access logs for unusual patterns or requests from unexpected source IPs
Deploy endpoint detection solutions capable of identifying XSS attack patterns in IoT device traffic

Monitoring Recommendations

Enable comprehensive logging on the FIBARO Home Center and forward logs to a centralized SIEM
Monitor for authentication events following potential exploit attempts that may indicate session hijacking
Set up alerts for configuration changes on the Home Center that occur outside of normal administrative windows
Network segmentation monitoring to detect any lateral movement from compromised IoT controllers

How to Mitigate CVE-2020-36905

Immediate Actions Required

Update FIBARO System Home Center firmware to the latest available version that addresses this vulnerability
Place the Home Center behind a firewall and restrict network access to trusted IP addresses only
Disable or block access to the vulnerable proxy API endpoint if not required for operations
Review all connected IoT device configurations for unauthorized changes

Patch Information

Users should check the Fibaro Official Website for firmware updates that address this vulnerability. Ensure that automatic updates are enabled on the Home Center device to receive security patches promptly.

Additional technical details and advisory information can be found through:

Workarounds

Implement network segmentation to isolate the Home Center from untrusted networks and the public internet
Configure a reverse proxy with input validation rules in front of the Home Center web interface
Use Content Security Policy (CSP) headers at the network level to restrict script execution if possible
Limit user access to the Home Center administrative interface to reduce attack surface

bash

# Example firewall rule to restrict access to Home Center (adjust IP addresses accordingly)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP