CVE-2021-20168 in RAX43
Summary
by MITRE • 12/31/2021
Netgear RAX43 version 1.0.3.96 does not have sufficient protections to the UART interface. A malicious actor with physical access to the device is able to connect to the UART port via a serial connection, login with default credentials, and execute commands as the root user. These default credentials are admin:admin.
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Analysis
by VulDB Data Team • 01/05/2022
The vulnerability identified as CVE-2021-20168 affects Netgear RAX43 routers running firmware version 1.0.3.96 and represents a critical security flaw in the device's physical interface protection mechanisms. This vulnerability resides in the Universal Asynchronous Receiver-Transmitter (UART) interface, which serves as a low-level communication port typically used for debugging and system administration purposes during manufacturing and development phases. The flaw stems from insufficient security controls that fail to properly restrict access to this critical interface, creating an exploitable pathway for unauthorized individuals who gain physical possession of the device.
The technical implementation of this vulnerability demonstrates a classic case of inadequate physical security controls, specifically failing to implement proper authentication mechanisms for the UART interface. The device exposes the UART port without adequate protection measures, allowing any individual with physical access to establish a serial connection using standard serial communication tools. The default credential pair of admin:admin provides an easy target for exploitation, as these credentials are well-documented and commonly known within the security community. This weakness aligns with CWE-310, which addresses cryptographic weakness, and more specifically CWE-312, which deals with exposure of sensitive information through cleartext storage or transmission. The vulnerability essentially creates an attack surface that bypasses all network-based security controls, as the UART interface operates at a lower level than typical network protocols.
The operational impact of this vulnerability is severe and far-reaching, as it allows for complete system compromise with minimal technical expertise required from an attacker. Once physical access is obtained, an attacker can establish a serial connection and authenticate using the default credentials, immediately gaining root-level privileges on the device. This level of access enables the execution of arbitrary commands, complete system modification, and potential data exfiltration. The implications extend beyond the immediate device, as compromised routers can serve as entry points for broader network attacks, enabling lateral movement and persistent access to corporate or home networks. According to ATT&CK framework, this vulnerability maps to T1059.007 for Command and Scripting Interpreter and T1078.004 for Valid Accounts, as it exploits legitimate administrative access mechanisms that should be protected.
Mitigation strategies for this vulnerability must address both the immediate physical security concerns and the broader security posture of the affected devices. Organizations should implement strict physical access controls to prevent unauthorized individuals from obtaining physical access to network equipment, including securing device locations and implementing access logging mechanisms. Firmware updates from Netgear should be applied immediately to address the identified weakness, though the root cause requires proper UART interface protection mechanisms to be implemented at the hardware and software levels. Network administrators should consider disabling UART interfaces on production devices where possible, as these interfaces should only be enabled during manufacturing and testing phases. The vulnerability also highlights the importance of the principle of least privilege and demonstrates how default configurations can create significant security risks, reinforcing the need for security-by-design principles and proper security testing throughout the development lifecycle. Additionally, implementing device integrity checks and monitoring for unauthorized serial connections could provide early detection of exploitation attempts.