dbcve.org
Melsec Iq Rj71eip91 FirmwareOperating system · Mitsubishielectric

CVE-2020-5657

MEDIUM · 6.5 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 →
70/100
Remediation priority · Elevated
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
Improper neutralization of argument delimiters in a command ('Argument Injection') 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 unauthenticated attackers on adjacent network 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 · moderate confidence

This is an Argument Injection vulnerability in the TCP/IP function of multiple MELSEC iQ-R series firmware modules. Attackers on the adjacent network can send specially crafted packets with improperly neutralized argument delimiters to inject commands, allowing unauthenticated attackers to stop the network functions of affected modules.

MitigationCheck the serial number prefix of affected modules (02/01/08/04 depending on model) and apply vendor firmware updates when available. Implement network segmentation to restrict adjacent network access and monitor for attempts to exploit this vulnerability.

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/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
    Access the PLC/controller programming software (such as GX Works3) and review the hardware configuration or module list to identify if any of these modules are present: RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, or RD81OPC96
    Affected if Any of the five listed modules appear in the system configuration
  2. Confirm TCP/IP function is enabled
    Using the programming software, navigate to the module parameters for the identified MELSEC iQ-R module and check if the TCP/IP network function or Ethernet communication is configured and enabled in the module settings
    Affected if TCP/IP or Ethernet communication function is enabled in the module parameters
  3. Verify module has an IP address on the network
    Check the module network settings to confirm it has been assigned an IP address and is configured for communication on the industrial network
    Affected if The module has an active IP address and is configured for network communication
  4. Assess network accessibility from adjacent network
    Review network segmentation and firewall rules to determine if the PLC network where the module resides is accessible from adjacent networks (other subnetworks or untrusted network segments)
    Affected if The module is reachable from adjacent network segments without proper network isolation

If a MELSEC iQ-R module from the affected list (RJ71EIP91, RJ71PN92, RD81DL96, RD81MES96N, or RD81OPC96) is present with TCP/IP enabled and accessible from adjacent networks, the environment is vulnerable to CVE-2020-5657.

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

Check the serial number prefix of affected modules (02/01/08/04 depending on model) and apply vendor firmware updates when available. Implement network segmentation to restrict adjacent network access and monitor for attempts to exploit this vulnerability.

Fix this in Melsec Iq Rj71eip91 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-5657 — 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-2020-5657 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