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R00cpu FirmwareOperating system · Mitsubishielectric

CVE-2020-5668

HIGH · 7.5 CVSS v3.1 Published 2020-11-20
Fix available
A fix is available. Upgrade to after 51 or later.
See remediation →
84/100
Remediation priority · High
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
Uncontrolled resource consumption vulnerability in MELSEC iQ-R Series modules (R00/01/02CPU firmware version '19' and earlier, R04/08/16/32/120 (EN) CPU firmware version '51' and earlier, R08/16/32/120SFCPU firmware version '22' and earlier, R08/16/32/120PCPU firmware version '25' and earlier, R08/16/32/120PSFCPU firmware version '06' and earlier, RJ71EN71 firmware version '47' and earlier, RJ71GF11-T2 firmware version '47' and earlier, RJ72GF15-T2 firmware version '07' and earlier, RJ71GP21-SX firmware version '47' and earlier, RJ71GP21S-SX firmware version '47' and earlier, and RJ71GN11-T2 firmware version '11' and earlier) allows a remote unauthenticated attacker to cause an error in a CPU unit and cause a denial-of-service (DoS) condition in execution of the program and its communication, or to cause a denial-of-service (DoS) condition in communication via the unit by receiving a specially crafted SLMP packet

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 MELSEC iQ-R Series PLC modules contain an uncontrolled resource consumption vulnerability where specially crafted SLMP packets can cause CPU errors leading to denial of service. The vulnerability is exploitable remotely by unauthenticated attackers.

MitigationUpdate firmware to versions beyond those specified (R00/01/02CPU to '20'+, R04/08/16/32/120EN CPU to '52'+, RJ71EN71 to '48'+, RJ71GF11-T2 to '48'+, etc.) and implement network segmentation to restrict SLMP access to trusted sources only.

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
R00cpu FirmwareOperating system
Affected:<= 19
R01cpu FirmwareOperating system
Affected:<= 19
R02cpu FirmwareOperating system
Affected:<= 19
R04cpu FirmwareOperating system
Affected:<= 51
R08cpu FirmwareOperating system
Affected:<= 51
R16cpu FirmwareOperating system
Affected:<= 51
R32cpu FirmwareOperating system
Affected:<= 51
R120cpu FirmwareOperating system
Affected:<= 51

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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. Identify the PLC CPU model
    Determine if the target device is a Mitsubishi MELSEC iQ-R Series PLC (R00CPU, R01CPU, R02CPU, R04CPU, R08CPU, R16CPU, R32CPU, or R120CPU). Check the module labeling or consult the engineering project configuration in GX Works3.
    Affected if The device is any of the listed CPU models (R00cpu through R120cpu).
  2. Check the firmware version
    Retrieve the current firmware version from the PLC CPU module. This is typically accessible through GX Works3 under CPU module diagnostics, the module's web interface, or the system information display. Compare the installed version against the affected ranges.
    Affected if Firmware version is 19 or lower for R00/01/02CPU, or 51 or lower for R04/08/16/32/120CPU.
  3. Verify SLMP protocol status
    Determine whether the SLMP (Seamless Message Protocol) communication function is enabled on the PLC. Check the PLC parameters in GX Works3 under the Ethernet port settings or SLMP configuration. Confirm if the SLMP server/listener is active.
    Affected if SLMP communication is enabled and accessible on the network.
  4. Assess network exposure of SLMP service
    Identify if the SLMP service (typically port 5007/tcp or 5006/tcp) is exposed beyond the trusted network segment. Review firewall rules, network segmentation, and access control lists to determine if unauthenticated remote access is possible.
    Affected if SLMP ports are reachable from untrusted network segments or the internet.

You are affected if you have a vulnerable R-series CPU (R00/01/02 with firmware <=19, or R04/08/16/32/120 with firmware <=51) with SLMP protocol enabled and accessible from an untrusted network.

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
Upgrade available Upgrade to a release after 51
Interim mitigation

Update firmware to versions beyond those specified (R00/01/02CPU to '20'+, R04/08/16/32/120EN CPU to '52'+, RJ71EN71 to '48'+, RJ71GF11-T2 to '48'+, etc.) and implement network segmentation to restrict SLMP access to trusted sources only.

Fix this in R00cpu Firmware Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA8.0 h
44.0 hours of engineering $7,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.

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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-2020-5668 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data