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Melsec Iq R FirmwareOperating system · Mitsubishielectric

CVE-2020-5594

CRITICAL · 9.8 CVSS v3.1 Published 2020-06-23
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Mitsubishi Electric MELSEC iQ-R, iQ-F, Q, L, and FX series CPU modules all versions contain a vulnerability that allows cleartext transmission of sensitive information between CPU modules and GX Works3 and/or GX Works2 via unspecified vectors.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Mitsubishi Electric MELSEC PLC CPU modules (iQ-R, iQ-F, Q, L, and FX series) transmit sensitive information in cleartext between the CPU modules and the GX Works3/GX Works2 engineering workstations. This allows unauthenticated attackers on the network to intercept potentially privileged credentials, configuration data, or proprietary program logic communicated during engineering sessions.

MitigationEnable encrypted communication protocols supported by the affected CPU modules and engineering workstations, apply any available firmware/software updates from Mitsubishi Electric, and implement network segmentation to isolate engineering workstation traffic from untrusted networks.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Melsec Iq R FirmwareOperating system
Affected:all versions
Melsec Iq F FirmwareOperating system
Affected:all versions
Melsec Q FirmwareOperating system
Affected:all versions
Melsec L FirmwareOperating system
Affected:all versions
Melsec Fx FirmwareOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify PLC communication protocol settings
    Access the PLC CPU module configuration via GX Works3 or GX Works2. Navigate to the CPU module's communication settings and check whether encrypted protocols (such as SSL/TLS-based communication) are enabled or if only unencrypted protocols (such as TCP/IP without encryption) are configured.
    Affected if The PLC is configured to use unencrypted communication protocols or if the encryption option is disabled/not configured.
  2. Check engineering workstation connection configuration
    In GX Works3 or GX Works2, examine the connection destination settings for each engineering session. Verify whether the connection is set to use encrypted communication or standard unencrypted Ethernet communication with the PLC.
    Affected if The engineering workstation is configured to connect using standard Ethernet without encryption enabled.
  3. Inspect network traffic between PLC and engineering workstation
    Use a network packet capture tool (such as Wireshark) on the network segment between the PLC CPU module and the engineering workstation. Capture and analyze the traffic to identify if sensitive data (credentials, configuration, program logic) is transmitted in cleartext rather than encrypted.
    Affected if Network captures show plaintext traffic containing authentication credentials, configuration data, or program logic traversing the network without encryption.
  4. Confirm PLC model and series
    Identify the specific PLC CPU module model (iQ-R, iQ-F, Q, L, or FX series) by checking the module labeling or via GX Works3/GX Works2 system information. Confirm it is a Mitsubishi Electric MELSEC PLC.
    Affected if The device is a Mitsubishi Electric MELSEC PLC CPU module from the iQ-R, iQ-F, Q, L, or FX series.

If the PLC uses unencrypted communication protocols and the network traffic contains cleartext sensitive data, the environment is affected by this CVE.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Enable encrypted communication protocols supported by the affected CPU modules and engineering workstations, apply any available firmware/software updates from Mitsubishi Electric, and implement network segmentation to isolate engineering workstation traffic from untrusted networks.

Fix this in Melsec Iq R Firmware Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA4.0 h
40.0 hours of engineering $7,000
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-5594 in production — separate from our analysis above.

No notes yet

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data