CVE-2021-46559 in TN-5900
Summary
by MITRE • 01/26/2022
The firmware on Moxa TN-5900 devices through 3.1 has a weak algorithm that allows an attacker to defeat an inspection mechanism for integrity protection.
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Analysis
by VulDB Data Team • 01/29/2022
The vulnerability identified as CVE-2021-46559 affects Moxa TN-5900 industrial network devices running firmware versions through 3.1, representing a critical weakness in the device's integrity protection mechanisms. This issue stems from the implementation of a weak cryptographic algorithm within the device's firmware update and verification processes, which fundamentally undermines the security posture of these industrial control systems. The affected devices operate in environments where network reliability and security are paramount, making this vulnerability particularly concerning for critical infrastructure deployments.
The technical flaw manifests in the firmware's use of insufficiently strong cryptographic primitives that can be easily reverse-engineered or brute-forced by attackers with moderate resources. This weakness directly impacts the device's ability to verify the integrity of firmware updates and system components, creating a pathway for malicious actors to inject unauthorized code or modify existing firmware without detection. The vulnerability essentially provides a backdoor mechanism that bypasses the intended security controls designed to prevent unauthorized modifications to the device's operational software. From a cybersecurity perspective, this represents a failure in the principle of least privilege and integrity verification that are fundamental to secure system design.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it enables attackers to potentially compromise entire industrial networks through these vulnerable devices. The TN-5900 series devices are commonly deployed in industrial environments where they serve as network gateways, protocol converters, and communication bridges between different system components. An attacker who successfully exploits this weakness could gain persistent access to the network, potentially leading to data exfiltration, system disruption, or even physical damage to industrial processes. The implications are particularly severe in critical infrastructure sectors such as energy, water treatment, and manufacturing where these devices play crucial roles in operational technology networks. This vulnerability also aligns with attack patterns described in the MITRE ATT&CK framework under the 'Defense Evasion' and 'Persistence' tactics, as it enables both unauthorized code execution and long-term access to compromised systems.
Organizations should implement immediate mitigations including firmware updates from Moxa when available, network segmentation to limit access to these devices, and enhanced monitoring of network traffic for suspicious activities. The vulnerability demonstrates the importance of strong cryptographic practices in embedded systems and aligns with CWE-327, which addresses the use of weak cryptographic algorithms. Security teams should also consider implementing additional layers of protection such as network access controls, regular security assessments, and continuous monitoring of device behavior to detect potential exploitation attempts. Given the industrial nature of these deployments, organizations must also evaluate their overall operational technology security posture and ensure that security controls are appropriately adapted to protect against both traditional cybersecurity threats and specialized industrial attacks that may target these specific device types.