CVE-2016-8368 in MELSEC-Q
Summary
by MITRE
An issue was discovered in Mitsubishi Electric Automation MELSEC-Q series Ethernet interface modules QJ71E71-100, all versions, QJ71E71-B5, all versions, and QJ71E71-B2, all versions. The affected Ethernet interface module is connected to a MELSEC-Q PLC, which may allow a remote attacker to connect to the PLC via Port 5002/TCP and cause a denial of service, requiring the PLC to be reset to resume operation. This is caused by an Unrestricted Externally Accessible Lock.
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Analysis
by VulDB Data Team • 09/02/2020
The vulnerability identified as CVE-2016-8368 affects Mitsubishi Electric Automation's MELSEC-Q series Ethernet interface modules, specifically the QJ71E71-100, QJ71E71-B5, and QJ71E71-B2 models across all versions. This security flaw represents a critical weakness in industrial control systems where the affected Ethernet interface modules maintain an externally accessible lock mechanism that lacks proper access restrictions. The vulnerability manifests through the module's exposure of port 5002/tcp, which serves as an entry point for remote attackers to gain unauthorized access to the connected MELSEC-Q PLC systems. This design flaw creates an unrestricted externally accessible lock condition that directly violates fundamental security principles for industrial automation systems.
The technical implementation of this vulnerability stems from the Ethernet interface modules' failure to properly implement authentication mechanisms or access controls for their communication protocols. When attackers connect to port 5002/tcp, they can exploit the unrestricted lock mechanism to establish connections to the PLC, potentially leading to system disruption. This vulnerability operates at the network layer and affects the operational integrity of industrial control systems by allowing unauthorized remote access that can result in complete system unavailability. The flaw essentially provides a backdoor that bypasses normal security controls, enabling attackers to manipulate the PLC's operational state without proper authorization.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it fundamentally compromises the security posture of industrial control systems. When exploited, the vulnerability forces the PLC to enter a state requiring manual reset operations, which can result in significant production downtime and potential safety hazards in critical infrastructure environments. The requirement for system reset represents a serious operational disruption that can affect manufacturing processes, process control systems, and other industrial applications where continuous operation is essential. This vulnerability directly impacts the availability and reliability of industrial control systems, potentially leading to cascading effects throughout connected processes and operations.
Organizations should implement immediate mitigation strategies including network segmentation to isolate affected Ethernet interface modules from untrusted networks, firewall rules to block external access to port 5002/tcp, and network monitoring to detect unauthorized connection attempts. The vulnerability aligns with CWE-284 which addresses improper access control, and represents a significant concern under the ATT&CK framework's privilege escalation and defense evasion techniques. System administrators should also consider applying manufacturer-provided firmware updates when available, implementing network access controls, and establishing monitoring procedures to detect potential exploitation attempts. This vulnerability demonstrates the critical importance of securing industrial control systems against remote attack vectors and highlights the need for comprehensive security assessments of industrial automation infrastructure.