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Mitsubishi Electric MELSEC iQ-F Series

Monitor7.4ICS-CERT ICSA-20-345-01Dec 10, 2020
Attack VectorAdjacent
Auth RequiredNone
ComplexityLow
User InteractionNone needed
Summary

A denial-of-service vulnerability exists in Mitsubishi Electric MELSEC iQ-F Series FX5U(C) CPU module firmware versions 1.060 and earlier. Successful exploitation causes the CPU module to enter a denial-of-service condition where the device stops responding to input/output and control requests. Recovery requires a manual reset of the CPU module. The vulnerability is reachable from the local network segment with no authentication required.

What this means
What could happen
An attacker on the same network segment could cause the PLC to stop responding, halting all control logic and automation until the CPU is manually reset. This would interrupt water treatment, power distribution, or other critical processes depending on what the PLC controls.
Who's at risk
Water utilities, municipal electric utilities, and other critical infrastructure operators using Mitsubishi Electric MELSEC iQ-F series FX5U(C) CPU modules for process automation and control. The vulnerability affects the core PLC that manages pumps, motors, valve automation, or power distribution logic.
How it could be exploited
An attacker with access to the same network segment as the MELSEC iQ-F CPU module could send a specially crafted packet to trigger a denial-of-service condition. The attack requires no authentication and causes the CPU to become unresponsive, requiring physical or remote reset to restore operation.
Prerequisites
  • Network access to the MELSEC iQ-F CPU module from the same network segment or LAN
  • No valid credentials required
Remotely exploitable over local networkNo authentication requiredNo patch availableCauses denial of service to critical control logicLow attack complexity
Exploitability
Low exploit probability (EPSS 0.2%)
Affected products (1)
ProductAffected VersionsFix Status
MELSEC iQ-F Series - FX5U(C) CPU module: firmware≤ 1.060No fix yet
Remediation & Mitigation
0/4
Do now
0/1
HARDENINGIsolate MELSEC iQ-F CPU modules on a dedicated control network segment with firewall rules restricting access to only authorized engineering workstations and SCADA servers
Schedule — requires maintenance window
0/2

Patching may require device reboot — plan for process interruption

WORKAROUNDMonitor network traffic to MELSEC iQ-F devices for unusual patterns or suspicious connections
HARDENINGEstablish and test a manual reset procedure for MELSEC iQ-F CPUs so operations staff can quickly restore the device if a denial-of-service event occurs
Long-term hardening
0/1
HARDENINGImplement network segmentation between corporate IT and operational technology networks using firewalls or air-gap architecture to prevent attackers from reaching the PLC
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Mitsubishi Electric MELSEC iQ-F Series | CVSS 7.4 - OTPulse