dbcve.org
Melsec Iq Rj71eip91 FirmwareOperating system · Mitsubishielectric

CVE-2020-5658

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
Resource Management Errors 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 resource management error in the TCP/IP stack of Mitsubishi MELSEC iQ-R series modules (RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, RD81OPC96) allows remote unauthenticated attackers to cause a denial of service by sending specially crafted packets, stopping network functions of the affected devices.

MitigationApply vendor firmware updates to affected modules (serial number constraints apply). If updates cannot be immediately applied, isolate affected devices behind firewalls and monitor for anomalous network traffic to mitigate exploitation.

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 installed MELSEC iQ-R modules
    Review the hardware configuration or system inventory to list all installed MELSEC iQ-R series modules. Look specifically for model numbers: RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, and RD81OPC96.
    Affected if Any of these five specific module model numbers are present in the system configuration
  2. Verify TCP/IP network functionality is enabled
    Access the module configuration via the engineering software (GX Works3) or module web interface. Check if the TCP/IP stack or network communication functions are configured and enabled for the identified modules.
    Affected if The identified module has TCP/IP or Ethernet communication functions enabled and is on the network
  3. Check network function status
    Monitor the module for network availability. Look for indicators of network function failure, unexpected disconnections, or loss of network communication that may indicate exploitation.
    Affected if Network functions are unresponsive, repeatedly failing, or the module shows denial of service symptoms after receiving network traffic
  4. Review network traffic for anomalies
    Use network monitoring tools to inspect incoming packets to the affected modules. Look for unusual or specially crafted packets that may indicate attempted exploitation.
    Affected if Suspicious or malformed packets are observed targeting the affected module's IP address

A system is affected if it has any of the five vulnerable module models (RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, RD81OPC96) with TCP/IP network functions enabled and experiencing or vulnerable to denial of service from crafted network packets.

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 firmware updates to affected modules (serial number constraints apply). If updates cannot be immediately applied, isolate affected devices behind firewalls and monitor for anomalous network traffic to mitigate exploitation.

Fix this in Melsec Iq Rj71eip91 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,150
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,440.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-5658 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-5658 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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