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Melsec Iq Rj71eip91 FirmwareOperating system · Mitsubishielectric

CVE-2020-5653

CRITICAL · 9.8 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 →
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
Buffer overflow vulnerability in TCP/IP function included in the firmware of MELSEC iQ-R series (RJ71EIP91 EtherNet/IP Network Interface Module First 2 digits of serial number are '02' or before, RJ71PN92 PROFINET IO Controller Module First 2 digits of serial number are '01' or before, RD81DL96 High Speed Data Logger Module First 2 digits of serial number are '08' or before, RD81MES96N MES Interface Module First 2 digits of serial number are '04' or before, and RD81OPC96 OPC UA Server Module First 2 digits of serial number are '04' or before) allows a remote unauthenticated attacker to stop the network functions of the products or execute a malicious program via a specially crafted 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

Buffer overflow vulnerability in the TCP/IP function of MELSEC iQ-R series firmware (multiple network interface modules including RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, and RD81OPC96) allows remote unauthenticated attackers to execute arbitrary code or cause denial of service via specially crafted network packets.

MitigationUpdate affected modules to firmware versions that address this vulnerability. If immediate updates are not possible, implement network segmentation, firewall rules, and disable or restrict access to affected network services to reduce attack surface.

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 Rj71eip91 FirmwareOperating system
Affected:all versions
Melsec Iq Rj71pn92 FirmwareOperating system
Affected:all versions
Melsec Iq Rd81dl96 FirmwareOperating system
Affected:all versions
Melsec Iq Rd81mes96n FirmwareOperating system
Affected:all versions
Melsec Iq Rd81opc96 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. Identify MELSEC iQ-R network modules in your environment
    Locate and inventory all network interface modules in your MELSEC iQ-R PLC system. Check the module part numbers physically or via the engineering software (GX Works3) against these models: RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, and RD81OPC96.
    Affected if Any of these five specific module part numbers are present in the environment.
  2. Verify network communication is enabled for the module
    In GX Works3, navigate to the module configuration and check if the TCP/IP function or network communication parameters are configured and enabled for the affected module.
    Affected if Network communication or TCP/IP function is enabled and configured on the module.
  3. Check network exposure of affected modules
    Review network architecture and firewall rules to determine if the PLC network containing these modules is accessible from external networks or untrusted zones.
    Affected if The module's network is reachable from untrusted or external network segments.
  4. Confirm module is actively running
    Check the PLC system status in GX Works3 or via the module's LED indicators to confirm the affected network module is in RUN or online status.
    Affected if The module is powered on and actively running on the network.

If any of the five affected module models (RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, RD81OPC96) are present in the environment with network communication enabled, the environment is affected by this CVE because all firmware versions of these modules are vulnerable.

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

Update affected modules to firmware versions that address this vulnerability. If immediate updates are not possible, implement network segmentation, firewall rules, and disable or restrict access to affected network services to reduce attack surface.

Fix this in Melsec Iq Rj71eip91 Firmware Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA6.0 h
42.0 hours of engineering $7,360
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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-2020-5653 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