CVE-2020-18756 in PLC MAC1100
Summary
by MITRE • 08/14/2021
An arbitrary memory access vulnerability in the EPA protocol of Dut Computer Control Engineering Co.'s PLC MAC1100 allows attackers to read the contents of any variable area.
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Analysis
by VulDB Data Team • 08/18/2021
The CVE-2020-18756 vulnerability represents a critical security flaw in the EPA protocol implementation of Dut Computer Control Engineering Co.'s PLC MAC1100 industrial control device. This vulnerability falls under the category of improper access control and memory handling issues, specifically manifesting as an arbitrary memory access vulnerability that fundamentally compromises the integrity and confidentiality of industrial control systems. The flaw exists within the communication protocol stack of the MAC1100 PLC, which is widely deployed in industrial environments for process control and automation. The vulnerability allows unauthorized parties to access any variable area within the device's memory, effectively bypassing the normal access controls and security boundaries that should protect sensitive operational data.
The technical implementation of this vulnerability stems from inadequate input validation and memory access controls within the EPA protocol handler. When the PLC receives specially crafted protocol messages, it fails to properly validate the memory addresses specified in the requests, allowing attackers to specify arbitrary memory locations for reading operations. This type of vulnerability is classified as CWE-125: "Out-of-bounds Read" and can be categorized under the broader ATT&CK technique T1071.004: "Application Layer Protocol: DNS" when considering the protocol manipulation aspects, though in this case the protocol is the EPA communication layer itself. The flaw essentially creates a backdoor through which attackers can extract sensitive operational data, configuration parameters, and process variables that should remain protected within the industrial control system.
The operational impact of this vulnerability extends far beyond simple data exposure, as it enables attackers to gain comprehensive visibility into industrial processes and potentially manipulate system behavior. An attacker with access to variable areas can extract process parameters, control logic, and operational settings that may reveal critical infrastructure information. This capability directly threatens the security posture of industrial environments, as it allows for reconnaissance activities that could lead to more sophisticated attacks. The vulnerability is particularly concerning in critical infrastructure settings where PLCs control manufacturing processes, power generation, or other essential services. Attackers could use this information to develop targeted attacks against specific industrial processes, potentially causing operational disruptions, safety hazards, or economic damage. The impact is amplified by the fact that this vulnerability affects a widely deployed PLC model, meaning that numerous industrial facilities may be potentially compromised.
Mitigation strategies for CVE-2020-18756 should focus on both immediate remediation and long-term security hardening measures. Organizations should prioritize applying vendor patches or firmware updates as soon as they become available, though it's important to note that the manufacturer may have ceased support for this specific model. Network segmentation and access control measures should be implemented to limit direct communication with the affected PLCs, particularly through the EPA protocol. Implementing network monitoring and anomaly detection systems can help identify suspicious protocol activity that may indicate exploitation attempts. Regular security assessments of industrial control systems should include vulnerability scanning for similar protocol implementations, as this vulnerability pattern may exist in other industrial devices. The security community should also consider implementing secure communication protocols and encryption for industrial communications to prevent unauthorized access. Additionally, organizations should maintain comprehensive operational technology (OT) security programs that include regular vulnerability assessments, security monitoring, and incident response procedures specifically tailored for industrial environments. This vulnerability underscores the importance of applying security principles to industrial control systems and highlights the need for continuous vigilance in protecting critical infrastructure from evolving cyber threats.