CVE-2020-8157 in Cloud Key
Summary
by MITRE
UniFi Cloud Key firmware <= v1.1.10 for Cloud Key gen2 and Cloud Key gen2 Plus contains a vulnerability that allows unrestricted root access through the serial interface (UART).
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 10/15/2020
The UniFi Cloud Key firmware vulnerability identified as CVE-2020-8157 represents a critical security flaw affecting Cloud Key gen2 and Cloud Key gen2 Plus devices running firmware versions up to v1.1.10. This vulnerability exposes a fundamental weakness in the device's physical security model by allowing unauthorized root access through the serial interface, commonly known as the Universal Asynchronous Receiver-Transmitter (UART) port. The issue stems from inadequate protection mechanisms that fail to properly secure the serial communication channel, which serves as a direct pathway to the device's underlying operating system and administrative privileges.
The technical implementation of this vulnerability involves the absence of proper authentication controls at the UART interface level, enabling any individual with physical access to the device to establish a serial connection and gain unrestricted root privileges. This flaw operates at the hardware level rather than through network-based attacks, making it particularly concerning for security-conscious environments where physical security measures may be insufficient or compromised. The vulnerability falls under the category of improper access control as defined by CWE-284, specifically targeting the unauthorized access to privileged system resources through physical interfaces.
From an operational perspective, this vulnerability creates severe implications for network security infrastructure deployments that rely on UniFi Cloud Key devices for centralized management and monitoring. Attackers with physical access to the device can bypass all network-based security controls and gain complete administrative control over the device, potentially enabling them to modify configurations, extract sensitive data, or establish persistent backdoors. The impact extends beyond the individual device to affect the broader network security posture, as compromised Cloud Key devices can serve as entry points for lateral movement within the network infrastructure. This vulnerability aligns with ATT&CK technique T1018 for Valid Accounts and T1059 for Command and Scripting Interpreter, as it allows for command execution with root privileges and provides access to legitimate system accounts.
The exploitation of this vulnerability requires only physical access to the device and basic serial communication tools, making it particularly dangerous in environments where device security is not properly enforced. Organizations deploying these devices in unsecured locations or failing to implement proper physical security controls face significant risk of compromise. The vulnerability demonstrates a critical failure in the principle of least privilege, where the device's serial interface should require authentication or be completely secured against unauthorized access. Security practitioners should note that this vulnerability affects a wide range of network management and security monitoring devices, emphasizing the importance of firmware updates and physical security measures in protecting critical infrastructure components. The recommended mitigation involves immediate firmware updates to versions that address the UART access control issues, alongside implementation of physical security measures such as securing device enclosures and restricting access to administrative interfaces.