CVE-2019-10120 in Homematic CCU2
Summary
by MITRE
On eQ-3 HomeMatic CCU2 devices before 2.41.8 and CCU3 devices before 3.43.16, automatic login configuration (aka setAutoLogin) can be achieved by continuing to use a session ID after a logout, aka HMCCU-154.
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Analysis
by VulDB Data Team • 10/24/2023
The vulnerability described in CVE-2019-10120 affects eQ-3 HomeMatic CCU2 and CCU3 home automation devices, representing a critical session management flaw that undermines the security of automated home systems. This issue stems from improper handling of authentication state after user logout, creating a persistent security risk that allows unauthorized access through session replay attacks. The vulnerability specifically impacts devices running firmware versions prior to 2.41.8 for CCU2 and 3.43.16 for CCU3, leaving millions of home automation systems potentially exposed to malicious actors who can exploit this weakness to gain unauthorized control over connected devices and home networks.
The technical flaw manifests in the automatic login configuration mechanism, where the system fails to properly invalidate session identifiers upon user logout. This creates a scenario where an attacker can continue using a valid session ID to access the device's administrative interface even after legitimate logout operations have occurred. The vulnerability operates at the application layer, specifically within the authentication and session management components of the HomeMatic control unit software. This weakness falls under CWE-613, which addresses inadequate session management and improper session invalidation, making it particularly dangerous as it allows persistent access without requiring additional authentication credentials or exploiting other vulnerabilities. The session ID persistence creates a window of opportunity for attackers to maintain unauthorized access indefinitely until the session expires naturally or the device is rebooted.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it compromises the entire security posture of home automation ecosystems that rely on these devices for critical infrastructure control. Attackers can manipulate connected home devices including heating systems, security cameras, door locks, and lighting controls, potentially leading to privacy breaches, physical security risks, and unauthorized energy consumption. The vulnerability enables persistent access that could go undetected for extended periods, allowing attackers to monitor home activities, modify system configurations, or execute malicious commands against connected IoT devices. This represents a significant concern for the Internet of Things security landscape, as it demonstrates how legacy home automation systems can contain fundamental authentication flaws that persist across multiple firmware versions.
Mitigation strategies for this vulnerability require immediate firmware updates to the affected device versions, ensuring that all users upgrade to the patched releases that properly invalidate session identifiers upon logout operations. Network segmentation and access control measures should be implemented to limit exposure, while monitoring systems should be deployed to detect anomalous login patterns or unauthorized session usage. Security professionals should also consider implementing additional authentication layers such as two-factor authentication where available, and regularly audit device access logs to identify potential unauthorized access attempts. Organizations and individuals should follow the principle of least privilege by restricting administrative access to only necessary personnel and maintaining regular security assessments of their home automation infrastructure. The vulnerability highlights the importance of proper session management in embedded systems and reinforces the need for comprehensive security testing throughout the device lifecycle.