CVE-2020-19360 in FHEM
Summary
by MITRE • 01/20/2021
Local file inclusion in FHEM 6.0 allows in fhem/FileLog_logWrapper file parameter can allow an attacker to include a file, which can lead to sensitive information disclosure.
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Analysis
by VulDB Data Team • 02/15/2021
The vulnerability identified as CVE-2020-19360 represents a critical local file inclusion flaw within the FHEM home automation system version 6.0. This security weakness exists in the FileLog_logWrapper component where the file parameter is improperly validated, allowing malicious actors to manipulate file inclusion operations. The vulnerability stems from insufficient input sanitization and validation mechanisms that fail to properly filter or escape user-supplied data before processing. Attackers can exploit this weakness by crafting malicious requests that target the file parameter, enabling them to include arbitrary local files from the system. The affected FHEM environment operates with elevated privileges typically associated with the web server process, which means successful exploitation could result in unauthorized access to sensitive system files, configuration data, and potentially user credentials stored within the home automation environment.
The technical implementation of this vulnerability aligns with CWE-98, which specifically addresses the inclusion of files without proper validation, and falls under the broader category of CWE-22 related to improper limitation of a pathname to a restricted directory. The flaw manifests when the application processes user input through the file parameter without adequate sanitization, allowing path traversal sequences or absolute file paths to be injected. This creates an opportunity for attackers to access files outside the intended directory structure, potentially including system configuration files, database files, or other sensitive information. The exploitation typically involves appending directory traversal sequences such as ../ or ../../ to navigate the file system and access protected resources that should normally be restricted to authorized users only.
The operational impact of CVE-2020-19360 extends beyond simple information disclosure, as it represents a significant threat to the integrity and confidentiality of home automation environments that rely on FHEM for system management. Given that FHEM systems often control critical home infrastructure including security systems, lighting controls, and environmental monitoring, successful exploitation could enable attackers to gain comprehensive knowledge of the system architecture and potentially manipulate the automated processes. The vulnerability affects both authenticated and unauthenticated attackers, depending on the system configuration and access controls implemented. In environments where FHEM is deployed with default configurations or insufficient network segmentation, attackers could leverage this weakness to escalate privileges, access database contents, or potentially execute arbitrary code if the system allows for dynamic code execution in the context of file inclusion operations.
Mitigation strategies for this vulnerability should encompass multiple defensive layers following established security principles and frameworks. Organizations should immediately implement input validation controls that sanitize all user-supplied parameters, particularly those used in file inclusion operations, by employing allow-list validation techniques that only permit known good values. Network segmentation and access controls should be strengthened to limit direct exposure of FHEM systems to untrusted networks, while implementing proper authentication mechanisms and role-based access controls. The system should be configured to run with minimal required privileges, following the principle of least privilege to limit the potential damage from successful exploitation. Additionally, regular security updates and patches should be applied promptly, as this vulnerability has been addressed in subsequent versions of FHEM through proper input validation and parameter sanitization. Security monitoring should include detection of suspicious file access patterns and unusual network activity that might indicate exploitation attempts, while compliance with industry standards such as NIST SP 800-53 and ISO 27001 should be maintained through proper security control implementation and regular vulnerability assessments to prevent similar weaknesses from emerging in other components of the home automation infrastructure.