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Mitsubishi Electric GOC35 Series

Monitor7.5ICS-CERT ICSA-23-103-15Apr 14, 2023
Attack VectorNetwork
Auth RequiredNone
ComplexityLow
User InteractionNone needed
Summary

The GC-ENET-COM extension unit (Ethernet communication module for Mitsubishi Electric GOC35 series controllers) contains a vulnerability in units with serial numbers beginning with 16. Successful exploitation causes a communication error that results in a denial-of-service condition, disrupting the Ethernet link between the controller and connected field devices. Units with serial numbers beginning with 17 have been fixed; however, no firmware update is available for the vulnerable 16-series units.

What this means
What could happen
An attacker with network access to the GC-ENET-COM extension unit can trigger a communication error that causes a denial-of-service condition, interrupting the flow of data between the controller and connected devices and potentially halting operations.
Who's at risk
Energy utilities operating Mitsubishi Electric PLCs and I/O systems with GC-ENET-COM extension units should assess their installed base. This impacts any GC-ENET-COM communication modules with serial numbers starting with 16, which are commonly used to add Ethernet connectivity to GOC35 series controllers in power generation, distribution, and water treatment facilities.
How it could be exploited
An attacker sends a crafted network packet to the GC-ENET-COM extension unit, triggering a communication fault condition. This disrupts the Ethernet communication link between the controller and field devices, severing command and status updates until the device is restarted or the attack ceases.
Prerequisites
  • Network access to port 502 or other Modbus/industrial protocol port on the GC-ENET-COM unit
  • No authentication required
  • Target GC-ENET-COM serial number must begin with 16
remotely exploitableno authentication requiredlow complexityno patch available for affected serial numbers (16XXXXXXXXX)affects critical infrastructure communication
Exploitability
Low exploit probability (EPSS 0.4%)
Affected products (1)
ProductAffected VersionsFix Status
GC-ENET-COM: Models with the beginning serial number 16XXXXXXXXX.16XXXXXXXXX.No fix yet
Remediation & Mitigation
0/4
Do now
0/2
WORKAROUNDDeploy firewall rules to restrict network access to the GC-ENET-COM unit from untrusted networks and hosts
WORKAROUNDIf internet access to the GC-ENET-COM unit is required, use a VPN to encrypt and authenticate connections
Schedule — requires maintenance window
0/1

Patching may require device reboot — plan for process interruption

HOTFIXUpgrade firmware on GC-ENET-COM units with serial numbers beginning with 17 (fixed version available from Mitsubishi Electric India representatives)
Long-term hardening
0/1
HARDENINGIsolate control system network containing GC-ENET-COM units from the business network using air gaps, firewalls, or segmented VLANs
View full CISA ICS-CERT advisory
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