CVE-2019-9726 in Homematic CCU3
Summary
by MITRE
Directory Traversal / Arbitrary File Read in eQ-3 AG Homematic CCU3 3.43.15 and earlier allows remote attackers to read arbitrary files of the device's filesystem. This vulnerability can be exploited by unauthenticated attackers with access to the web interface.
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Analysis
by VulDB Data Team • 09/17/2023
The vulnerability identified as CVE-2019-9726 represents a critical directory traversal flaw in the eQ-3 AG Homematic CCU3 device firmware version 3.43.15 and earlier. This security weakness resides within the web interface component of the device, creating an exploitable condition that allows remote attackers to access arbitrary files from the underlying filesystem. The vulnerability specifically affects the device's handling of file path parameters, where insufficient input validation permits attackers to manipulate directory navigation sequences and gain unauthorized access to sensitive system files. The flaw enables attackers to bypass normal access controls and retrieve confidential information that should remain restricted to authorized users only.
The technical implementation of this vulnerability stems from improper sanitization of user-supplied input within the web application layer of the Homematic CCU3. When the device processes requests containing directory traversal sequences such as ../ or ..\, the system fails to adequately validate or sanitize these inputs before using them in file system operations. This deficiency creates a path traversal condition that allows attackers to navigate beyond the intended directory boundaries and access files that should be protected. The vulnerability manifests when the web interface processes file requests without proper authorization checks or input filtering mechanisms, enabling malicious actors to construct specific URLs or API calls that traverse the file system hierarchy.
From an operational perspective, this vulnerability poses significant risks to the security and integrity of Homematic CCU3 devices deployed in both residential and commercial environments. Attackers can exploit this weakness to read sensitive configuration files, authentication credentials, system logs, and other confidential data that may contain network credentials, device-specific information, or operational parameters. The impact extends beyond simple information disclosure, as the retrieved data could enable further exploitation attempts, including privilege escalation or lateral movement within networked environments. The fact that this vulnerability can be exploited by unauthenticated attackers with access to the web interface means that any device with the affected firmware version presents an open threat surface to potential adversaries.
The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. This classification reflects the core technical flaw where the application fails to properly validate user input before using it in file system operations. The attack pattern corresponds to techniques documented in the MITRE ATT&CK framework under the T1083 discovery technique, where adversaries attempt to gather information about the file system structure and access restricted files. Organizations using affected Homematic CCU3 devices face potential compromise of their smart home or building automation systems, with implications for both privacy and operational security.
Mitigation strategies for CVE-2019-9726 primarily involve firmware updates provided by eQ-3 AG to address the directory traversal vulnerability. System administrators should immediately upgrade to firmware versions that contain patches for this vulnerability, ensuring that all affected devices receive the necessary security fixes. Network segmentation and access control measures should be implemented to limit exposure of affected devices to untrusted networks, while monitoring systems should be deployed to detect suspicious file access patterns. Regular security assessments of IoT devices and comprehensive vulnerability management programs are essential for maintaining device security posture. Additionally, organizations should consider implementing network-based intrusion detection systems to monitor for exploitation attempts and maintain detailed audit logs of file access activities on affected systems.