CVE-2023-46033 in DSL-2750U N300 ADSL2+
Summary
by MITRE • 10/25/2023
** UNSUPPORTED WHEN ASSIGNED ** D-Link (Non-US) DSL-2750U N300 ADSL2+ and (Non-US) DSL-2730U N150 ADSL2+ are vulnerable to Incorrect Access Control. The UART/Serial interface on the PCB, provides log output and a root terminal without proper access control.
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Analysis
by VulDB Data Team • 08/03/2024
The vulnerability identified as CVE-2023-46033 affects D-Link DSL-2750U N300 ADSL2+ and DSL-2730U N150 ADSL2+ routers manufactured for non-US markets. These devices expose a UART/serial interface on their printed circuit board that provides both system log output and a root terminal access point. The flaw represents a critical security weakness that bypasses normal authentication mechanisms and grants unauthorized administrative access to the device's underlying operating system. This vulnerability stems from inadequate access control implementation within the device's firmware design, leaving the serial interface accessible without proper authorization checks. The UART interface typically serves as a debugging and diagnostic tool during manufacturing and development phases, but in this case, it remains exposed in production devices without proper security controls.
The technical implementation of this vulnerability involves the absence of proper access control mechanisms for the serial communication interface. The UART/serial port operates at the hardware level and provides direct access to the device's operating system through a root terminal session. This allows an attacker with physical access to the device to bypass all network-based authentication mechanisms and gain immediate administrative privileges. The vulnerability is particularly concerning because it operates at the lowest level of the device's architecture, making it extremely difficult to detect or mitigate through traditional network security measures. The lack of access control means that anyone who can connect to the serial interface can execute commands as the root user, potentially leading to complete device compromise and unauthorized network access.
The operational impact of this vulnerability extends beyond simple unauthorized access to include potential network infiltration and persistent backdoor establishment. An attacker with physical access to the device can use the root terminal to modify device configurations, install malicious firmware, or establish persistent access points. The vulnerability affects both the DSL-2750U N300 and DSL-2730U N150 models, suggesting a widespread issue within the D-Link product line for non-US markets. The exposure of system logs through the serial interface also provides attackers with detailed information about the device's operation, network configuration, and potentially sensitive data. This vulnerability aligns with CWE-284 Access Control Issues, specifically targeting improper access control mechanisms that allow unauthorized access to system resources. The flaw creates a persistent security risk that cannot be resolved through software patches alone, as the physical interface must be secured or disabled.
Mitigation strategies for this vulnerability require both physical and software-based approaches. Physical security measures should include disabling or securing the UART/serial interface through hardware modifications or protective covers that prevent unauthorized access to the interface. Network administrators should implement strict physical access controls for all network equipment, particularly devices that expose serial interfaces. Firmware updates from D-Link should be applied immediately if available, though the vulnerability may require hardware-level fixes that cannot be addressed through software patches alone. The security community should consider this vulnerability as a prime example of insufficient security by design principles, where debugging interfaces are not properly secured during the device's development lifecycle. Organizations should conduct comprehensive inventory audits to identify all affected devices and implement monitoring protocols to detect unauthorized physical access attempts. This vulnerability also highlights the importance of adhering to security standards such as NIST SP 800-53 and ISO 27001 controls for device security and access management, particularly in the context of embedded systems and IoT devices. The incident underscores the critical need for manufacturers to implement proper access control mechanisms for all interfaces, including debugging and diagnostic ports, during the initial design phase rather than addressing them as afterthoughts.