CVE-2018-7301 in Homematic CCU2
Summary
by MITRE
eQ-3 AG HomeMatic CCU2 2.29.22 devices have an open XML-RPC port without authentication. This can be exploited by sending arbitrary XML-RPC requests to control the attached BidCos devices.
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Analysis
by VulDB Data Team • 01/08/2020
The vulnerability identified as CVE-2018-7301 affects eQ-3 AG HomeMatic CCU2 devices running firmware version 2.29.22 and potentially earlier versions. This represents a critical security flaw in the HomeMatic home automation system that operates within residential and commercial environments. The affected devices expose an XML-RPC interface on a network port without implementing any form of authentication mechanism, creating an avenue for unauthorized access to the underlying home automation infrastructure. The vulnerability resides in the device's network configuration where the XML-RPC service listens for incoming connections without requiring credentials or access controls, effectively exposing the entire BidCos device management system to potential exploitation.
The technical nature of this vulnerability stems from the lack of authentication controls within the XML-RPC implementation on the CCU2 device. XML-RPC is a remote procedure call protocol that allows programs to execute procedures on remote systems, but when implemented without proper authentication mechanisms, it becomes a significant security risk. Attackers can leverage this flaw by simply sending malicious XML-RPC requests to the exposed port, bypassing any security measures that would normally prevent unauthorized access to the device's control functions. This allows for complete control over all BidCos devices connected to the system, including but not limited to lighting controls, heating systems, security sensors, and other connected home automation components. The vulnerability directly maps to CWE-284, which addresses improper access control issues, and represents a clear violation of the principle of least privilege in security design.
The operational impact of this vulnerability extends far beyond simple network access, as it provides attackers with comprehensive control over an entire home automation ecosystem. An attacker who discovers this open XML-RPC port can execute arbitrary commands against the CCU2 device, potentially leading to unauthorized device control, data manipulation, or even system compromise. The implications are particularly severe in residential settings where such systems control critical infrastructure like heating, lighting, and security systems. The vulnerability enables attackers to perform actions such as disabling security sensors, manipulating heating controls, or gaining unauthorized access to the home environment through connected devices. This represents a significant threat to both privacy and physical security, as the attacker could potentially gain complete visibility into the home automation system and its connected devices. The attack surface is further expanded by the fact that these devices are typically deployed in residential environments where network monitoring and security controls may be limited.
Mitigation strategies for CVE-2018-7301 should focus on immediate network-level protections and device configuration changes. The most effective immediate solution involves blocking access to the XML-RPC port at the network perimeter using firewalls or access control lists, preventing external access to the vulnerable service. Network segmentation should be implemented to isolate the HomeMatic CCU2 devices from public networks and limit access to authorized internal systems only. Device administrators should also consider disabling the XML-RPC interface entirely if it is not required for system operation, or implementing proper authentication mechanisms if the service must remain active. Additionally, regular firmware updates should be applied as soon as eQ-3 releases patches for this vulnerability, as the issue affects multiple versions of the HomeMatic CCU2 firmware. Organizations and individuals should also implement network monitoring to detect unauthorized access attempts to the XML-RPC interface and establish proper access controls through network access control lists and secure remote access protocols. This vulnerability highlights the importance of securing IoT devices and demonstrates how seemingly simple authentication flaws can lead to significant operational security risks in home automation environments. The issue aligns with ATT&CK technique T1071.004 for application layer protocol usage and T1046 for network service discovery, indicating that attackers may use these methods to identify and exploit such vulnerable services within their target environment.