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Melsec Q Q04udpvcpu FirmwareOperating system · Mitsubishielectric

CVE-2020-5652

HIGH · 7.5 CVSS v3.1 Published 2020-11-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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 Ethernet Port on MELSEC iQ-R, Q and L series CPU modules (R 00/01/02 CPU firmware versions '20' and earlier, R 04/08/16/32/120 (EN) CPU firmware versions '52' and earlier, R 08/16/32/120 SFCPU firmware versions '22' and earlier, R 08/16/32/120 PCPU all versions, R 08/16/32/120 PSFCPU all versions, R 16/32/64 MTCPU all versions, Q03 UDECPU, Q 04/06/10/13/20/26/50/100 UDEHCPU serial number '22081' and earlier , Q 03/04/06/13/26 UDVCPU serial number '22031' and earlier, Q 04/06/13/26 UDPVCPU serial number '22031' and earlier, Q 172/173 DCPU all versions, Q 172/173 DSCPU all versions, Q 170 MCPU all versions, Q 170 MSCPU all versions, L 02/06/26 CPU (-P) and L 26 CPU - (P) BT all versions) allows a remote unauthenticated attacker to stop the Ethernet communication functions of the products via a specially crafted packet, which may lead to a denial of service (DoS) condition .

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

This is an uncontrolled resource consumption vulnerability (CWE-400) in the Ethernet port of Mitsubishi MELSEC iQ-R, Q and L series PLC CPU modules. A remote unauthenticated attacker can send specially crafted packets that exhaust resources and cause the Ethernet communication functions to stop, resulting in denial of service.

MitigationApply available firmware updates from Mitsubishi Electric to address the vulnerability. If immediate patching is not possible, implement network segmentation, firewalls, or intrusion detection systems to limit exposure to untrusted networks, and monitor for signs of DoS conditions.

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 Q Q04udpvcpu FirmwareOperating system
Affected:= 22031
Melsec Q Q06udpvcpu FirmwareOperating system
Affected:= 22031
Melsec Q Q13udpvcpu FirmwareOperating system
Affected:= 22031
Melsec Q Q26udpvcpu FirmwareOperating system
Affected:= 22031
Melsec Q Q03udvcpu FirmwareOperating system
Affected:= 22031
Melsec Q Q04udvcpu FirmwareOperating system
Affected:= 22031
Melsec Q Q13udvcpu FirmwareOperating system
Affected:= 22031
Melsec Q Q26udvcpu FirmwareOperating system
Affected:= 22031

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 model
    Locate the physical PLC CPU module or check your system documentation to confirm the exact model number (e.g., Q04UDVCPU, Q06UDVCPU, Q13UDVCPU, Q26UDVCPU, Q04UDPVCPU, Q06UDPVCPU, Q13UDPVCPU, Q26UDPVCPU).
    Affected if The installed model matches one of the affected models listed in the CVE.
  2. Check the firmware version
    Use the MELSEC programming software (GX Works3) or the PLC's built-in web server to access the CPU module and view the firmware version information. The firmware version is typically displayed in the module diagnostics or product information screen.
    Affected if The firmware version is 22031.
  3. Verify Ethernet port is enabled
    Check the PLC configuration in GX Works3 under the Ethernet port settings. Confirm that the Ethernet communication function is enabled and configured.
    Affected if The Ethernet port is enabled and configured for use.
  4. Assess network exposure
    Review your network architecture to determine if the PLC's Ethernet interface is reachable from untrusted or external networks. Check firewall rules, VLAN configurations, and access control lists.
    Affected if The PLC's Ethernet port is accessible from untrusted or external networks without proper network segmentation or filtering.

You are affected if you have one of the listed Q series PLC models with firmware version 22031 and the Ethernet port is enabled and exposed to untrusted networks.

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

Apply available firmware updates from Mitsubishi Electric to address the vulnerability. If immediate patching is not possible, implement network segmentation, firewalls, or intrusion detection systems to limit exposure to untrusted networks, and monitor for signs of DoS conditions.

Fix this in Melsec Q Q04udpvcpu Firmware Scoped from the published advisory
  • Consultation3.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
17.0 hours of engineering $3,000
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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-2020-5652 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