CVE-2018-7299 in Homematic CCU2
Summary
by MITRE
Remote Code Execution in the addon installation process in eQ-3 AG Homematic CCU2 2.29.2 and earlier allows authenticated attackers to create or overwrite arbitrary files or install malicious software on the device.
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Analysis
by VulDB Data Team • 01/08/2020
The vulnerability identified as CVE-2018-7299 represents a critical remote code execution flaw within the eQ-3 AG Homematic CCU2 device firmware version 2.29.2 and earlier. This issue specifically targets the addon installation process, which serves as a legitimate mechanism for extending the functionality of the Homematic central control unit. The flaw allows authenticated attackers who have gained access to the device to exploit a directory traversal vulnerability during the addon installation procedure, enabling them to manipulate the file system in ways that were never intended by the developers. The vulnerability stems from inadequate input validation and sanitization within the installation process, creating a pathway for attackers to bypass normal security controls and execute arbitrary code with elevated privileges. This represents a significant concern for home automation systems where the central control unit serves as the primary interface for managing various smart home devices and security systems.
The technical exploitation of this vulnerability occurs through a carefully crafted addon installation request that leverages directory traversal techniques to manipulate file paths during the installation process. Attackers can leverage this flaw to create or overwrite arbitrary files on the device filesystem, potentially including system binaries, configuration files, or even malicious executables. The vulnerability is classified under CWE-22 as a directory traversal attack, which is a well-known weakness that allows attackers to access files and directories outside the intended scope. When combined with the authenticated access requirement, this creates a scenario where an attacker with legitimate credentials can escalate their privileges and gain complete control over the device. The attack vector involves manipulating the addon installation process to specify malicious file paths that bypass normal security checks, ultimately allowing the installation of unauthorized software that can persist across reboots and maintain access to the compromised system.
The operational impact of CVE-2018-7299 extends far beyond simple unauthorized file manipulation, as it provides attackers with complete control over the Homematic CCU2 device and potentially the entire smart home ecosystem it manages. This vulnerability allows for persistent backdoor installation, which can remain undetected while providing attackers with ongoing access to the network infrastructure. The compromised device can be used as a pivot point for attacking other devices within the same network, potentially leading to widespread compromise of the entire home automation system. From an ATT&CK framework perspective, this vulnerability maps to multiple techniques including T1059 for command and script injection, T1078 for valid accounts, and T1547 for persistence mechanisms. The attack can result in data exfiltration from connected smart home devices, unauthorized control of automated systems, and potential physical security breaches if the compromised system controls access points or security monitoring devices. Organizations and individuals relying on Homematic systems for home automation face significant risks including privacy violations, unauthorized access to personal data, and potential physical safety concerns if critical systems are compromised.
Mitigation strategies for CVE-2018-7299 should focus on immediate firmware updates to versions that address the directory traversal vulnerability in the addon installation process. System administrators should ensure that all Homematic CCU2 devices are updated to firmware version 2.30.17 or later, which includes patches specifically designed to prevent directory traversal attacks during addon installation. Network segmentation should be implemented to isolate smart home devices from critical network infrastructure, limiting the potential impact of a successful compromise. Access controls must be strictly enforced, with strong authentication mechanisms including multi-factor authentication where possible, to prevent unauthorized access to the device management interfaces. Regular security audits of smart home ecosystems should be conducted to identify and remediate similar vulnerabilities in other connected devices. Additionally, network monitoring should be implemented to detect unusual addon installation patterns or file system modifications that could indicate exploitation attempts. The vulnerability highlights the importance of secure coding practices in embedded systems and the need for comprehensive input validation and sanitization in all file manipulation processes, particularly in devices that serve as central control points for critical infrastructure.