Security Experts:

Flaw Exposes Mitsubishi PLCs to Remote DoS Attacks

Researchers discovered that some programmable logic controllers (PLCs) made by Japanese electrical equipment maker Mitsubishi Electric are affected by a serious denial-of-service (DoS) vulnerability.

The impacted devices are Mitsubishi Electric MELSEC-Q series PLCs, specifically QJ71E71-100 Ethernet interface modules with the serial number 20121 and prior. These PLCs are used worldwide in manufacturing facilities.

Mitsubishi Electric MELSEC-Q PLC vulnerabilityResearchers at industrial cybersecurity firm Nozomi Networks discovered that the PLCs are affected by a DoS vulnerability that can be exploited remotely by sending specially crafted TCP packets to the target’s FTP service.

“Successful exploitation of the vulnerability could allow a remote attacker to render the PLC’s state in fault mode, requiring a cold restart for recovering the system and/or doing privilege escalation or execute arbitrary code in the context of the affected system of the workstation engineering software,” Moreno Carullo, Nozomi Networks co-founder and CTO, told SecurityWeek.

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While in theory the flaw can be exploited remotely from the internet, Nozomi told SecurityWeek that it has not found any internet-exposed Q-series device using common services such as Shodan, ZoomEye and FOFA Pro.

The flaw is tracked as CVE-2019-10977 and it has been classified as “high severity” with a CVSS score of 7.5. DoS vulnerabilities are known to pose a bigger risk to industrial environments.

Mitsubishi Electric has addressed the vulnerability with the release of firmware version 20122 for the QJ71E71-100 Ethernet module. In addition, organizations can implement a series of mitigations recommended by the DHS's National Cybersecurity and Communications Integration Center (NCCIC).

“Minimize network exposure for all control system devices and/or systems, and ensure that they are not accessible from the Internet; Locate control system networks and remote devices behind firewalls,and isolate them from the business network; When remote access is required, use secure methods, such as Virtual Private Networks (VPNs), recognizing that VPNs may also have vulnerabilities and should be updated to the most current versions available. Also recognize that VPN is only as secure as the connected devices,” Carullo said.

Related: Critical Vulnerabilities Found in Mitsubishi HMI Tool

Related: Mitsubishi Develops Cybersecurity Technology for Cars

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.