CVE-2019-14926 in ME-RTU
Summary
by MITRE
An issue was discovered on Mitsubishi Electric ME-RTU devices through 2.02 and INEA ME-RTU devices through 3.0. Hard-coded SSH keys allow an attacker to gain unauthorised access or disclose encrypted data on the RTU due to the keys not being regenerated on initial installation or with firmware updates. In other words, these devices use private-key values in /etc/ssh/ssh_host_rsa_key, /etc/ssh/ssh_host_ecdsa_key, and /etc/ssh/ssh_host_dsa_key files that are publicly available from the vendor web sites.
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Analysis
by VulDB Data Team • 09/10/2024
The vulnerability identified as CVE-2019-14926 represents a critical security flaw affecting Mitsubishi Electric ME-RTU and INEA ME-RTU devices across multiple firmware versions. This weakness stems from the improper implementation of cryptographic key management within industrial control systems, specifically targeting the Secure Shell protocol configuration. The flaw manifests through the inclusion of hard-coded private keys within the device firmware, which are embedded in standard SSH host key files located at /etc/ssh/ssh_host_rsa_key, /etc/ssh/ssh_host_ecdsa_key, and /etc/ssh/ssh_host_dsa_key. These keys are not regenerated during initial device installation or firmware updates, creating a persistent security vulnerability that undermines the fundamental principles of secure remote access.
The technical implementation of this vulnerability aligns with CWE-326, which addresses the use of weak encryption algorithms and improper key management practices. The hard-coded keys represent a severe deviation from security best practices, as they eliminate the cryptographic entropy necessary for secure authentication. Attackers can exploit this weakness by simply accessing the publicly available keys from vendor websites and using them to establish unauthorized SSH sessions with the affected devices. This creates a direct pathway for privilege escalation and data exfiltration, as the attacker can bypass normal authentication mechanisms and gain root-level access to the industrial control system. The vulnerability is particularly concerning because it affects devices that are typically deployed in critical infrastructure environments where security is paramount.
From an operational perspective, this vulnerability exposes industrial control systems to significant risk of compromise, potentially enabling attackers to manipulate critical processes or extract sensitive operational data. The impact extends beyond simple unauthorized access, as the vulnerability can facilitate advanced persistent threats that may remain undetected for extended periods. Security professionals should note that this weakness creates a persistent backdoor that remains active regardless of password changes or other authentication measures. The attack surface is particularly broad given that these devices are commonly found in manufacturing environments, power generation facilities, and other critical infrastructure sectors. Organizations must consider the potential for cascading effects if compromised devices are part of larger network architectures, as the vulnerability could enable lateral movement within industrial networks.
The recommended mitigation strategies involve immediate firmware updates from Mitsubishi Electric to address the hard-coded key issue, though organizations should also implement network segmentation and monitoring to detect unauthorized access attempts. Additional protective measures include disabling SSH access where possible, implementing network-based access controls, and establishing robust logging mechanisms to detect suspicious activities. Security teams should also consider deploying intrusion detection systems specifically designed for industrial environments to monitor for exploitation attempts. The vulnerability demonstrates the importance of proper key lifecycle management in embedded systems and highlights the need for vendors to implement secure boot processes that generate unique cryptographic keys during device initialization. Organizations should conduct comprehensive risk assessments to identify all affected devices and establish remediation timelines that align with their operational requirements while maintaining security posture. This vulnerability serves as a reminder of the critical importance of cryptographic hygiene in industrial control systems and the potential consequences of failing to implement proper key management practices in critical infrastructure environments.