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Melsec Iq Rj71eip91 FirmwareOperating system · Mitsubishielectric

CVE-2020-5654

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
Session fixation 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 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

A session fixation vulnerability exists in the TCP/IP function of multiple MELSEC iQ-R series firmware modules. The flaw allows a remote, unauthenticated attacker to send specially crafted packets that can stop network functions on affected modules, including the RJ71EIP91 EtherNet/IP, RJ71PN92 PROFINET IO, RD81DL96, RD81MES96N, and RD81OPC96 modules.

MitigationApply vendor-supplied firmware updates after verifying affected module serial numbers fall within the vulnerable ranges (02 or earlier for RJ71EIP91, 01 or earlier for RJ71PN92, 08 or earlier for RD81DL96, 04 or earlier for RD81MES96N and RD81OPC96). If updates are unavailable, consider network segmentation to limit exposure.

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
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 MELSEC iQ-R network modules in the system
    Inspect the PLC rack or engineering software (GX Works3) to list installed modules. Look for RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, or RD81OPC96 modules.
    Affected if Any of these five module types are present in the MELSEC iQ-R system configuration.
  2. Check firmware version of affected modules
    In GX Works3, right-click each module and select Product Information, or use the module's web interface or system monitor to retrieve the firmware version.
    Affected if The module firmware version matches any of the affected model numbers (all versions are vulnerable per the advisory).
  3. Verify TCP/IP network function is enabled
    Check the module parameters in GX Works3 under the network configuration settings. Confirm that the TCP/IP function parameter is set to 'Use' or enabled.
    Affected if TCP/IP function is enabled and the module is configured for network communication.
  4. Assess network accessibility of the module
    Determine if the affected module's IP address is reachable from external networks or untrusted segments. Check firewall rules, VLAN configuration, and network segmentation around the PLC network.
    Affected if The module's TCP/IP interface is accessible from networks outside the trusted control system zone.

If any of the five affected module types (RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, RD81OPC96) are installed with TCP/IP enabled and network-accessible, the environment is potentially affected by CVE-2020-5654.

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 vendor-supplied firmware updates after verifying affected module serial numbers fall within the vulnerable ranges (02 or earlier for RJ71EIP91, 01 or earlier for RJ71PN92, 08 or earlier for RD81DL96, 04 or earlier for RD81MES96N and RD81OPC96). If updates are unavailable, consider network segmentation to limit exposure.

Fix this in Melsec Iq Rj71eip91 Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2020-5654 in production — separate from our analysis above.

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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