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Cj2m Cpu35 FirmwareOperating system · Omron

CVE-2023-38744

HIGH · 7.5 CVSS v3.1 Published 2023-08-03
Fix available
A fix is available. Upgrade to after 3.04 or later.
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
Denial-of-service (DoS) vulnerability due to improper validation of specified type of input issue exists in the built-in EtherNet/IP port of the CJ Series CJ2 CPU unit and the communication function of the CS/CJ Series EtherNet/IP unit. If an affected product receives a packet which is specially crafted by a remote unauthenticated attacker, the unit of the affected product may fall into a denial-of-service (DoS) condition. Affected products/versions are as follows: CJ2M CPU Unit CJ2M-CPU3[] Unit version of the built-in EtherNet/IP section Ver. 2.18 and earlier, CJ2H CPU Unit CJ2H-CPU6[]-EIP Unit version of the built-in EtherNet/IP section Ver. 3.04 and earlier, CS/CJ Series EtherNet/IP Unit CS1W-EIP21 V3.04 and earlier, and CS/CJ Series EtherNet/IP Unit CJ1W-EIP21 V3.04 and earlier.

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 a denial-of-service vulnerability in Omron's CJ Series PLCs (CJ2 CPU units and CS/CJ EtherNet/IP units) where improper validation of input in the EtherNet/IP protocol stack allows remote unauthenticated attackers to crash the device by sending specially crafted packets.

MitigationIsolate affected devices behind firewalls or network segmentation to limit exposure to untrusted networks; apply vendor firmware updates (Ver. 2.19+ for CJ2M, Ver. 3.05+ for CJ2H/CS1W-EIP21/CJ1W-EIP21) when available.

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
Cj2m Cpu35 FirmwareOperating system
Affected:<= 2.18
Cj2m Cpu34 FirmwareOperating system
Affected:<= 2.18
Cj2m Cpu33 FirmwareOperating system
Affected:<= 2.18
Cj2m Cpu32 FirmwareOperating system
Affected:<= 2.18
Cj2m Cpu31 FirmwareOperating system
Affected:<= 2.18
Cj2h Cpu68 Eip FirmwareOperating system
Affected:<= 3.04
Cj2h Cpu67 Eip FirmwareOperating system
Affected:<= 3.04
Cj2h Cpu66 Eip FirmwareOperating system
Affected:<= 3.04

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 Omron CJ2 PLC on the network
    Scan the network for devices responding to EtherNet/IP (port 44818) or use industrial asset discovery tools (like nmap with enip-enumerate or Omron's network scanner) to identify Omron devices. Look for vendor ID 46 (Omron) in EtherNet/IP identity responses.
    Affected if An Omron CJ2 device is found responding on the network with EtherNet/IP enabled.
  2. Confirm the specific CJ2 model
    Query the device's EtherNet/IP identity object (0x01) or check the device nameplate/model number via CX-Programmer or the device web interface. Look for model numbers: CJ2M-CPU31 through CJ2M-CPU35, or CJ2H-CPU66 through CJ2H-CPU68 (EIP variant).
    Affected if The device model is CJ2M (CPU31-35) or CJ2H (CPU66-68) with EIP functionality.
  3. Check the firmware version
    Read the device's unit version or firmware revision via CX-Programmer (go online with the PLC, then System Information > Unit Version), through the device web interface if available, or via EtherNet/IP get attribute single requests to identity object attributes 5 (revision).
    Affected if The firmware version is 2.18 or lower for CJ2M models, or 3.04 or lower for CJ2H models.
  4. Verify EtherNet/IP is enabled
    Check the PLC configuration in CX-Programmer under CPU Unit Setup > Built-in EtherNet/IP or verify the CS/CJ EtherNet/IP unit is mounted and configured in the I/O table. The vulnerability affects the EtherNet/IP stack, so it only applies if this feature is active.
    Affected if EtherNet/IP functionality is enabled and operational on the device.

You are affected if you have an Omron CJ2M (firmware <=2.18) or CJ2H-EIP (firmware <=3.04) PLC with EtherNet/IP enabled, as these versions contain the vulnerable input validation in the EtherNet/IP protocol stack.

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
Upgrade available Upgrade to a release after 3.04
Interim mitigation

Isolate affected devices behind firewalls or network segmentation to limit exposure to untrusted networks; apply vendor firmware updates (Ver. 2.19+ for CJ2M, Ver. 3.05+ for CJ2H/CS1W-EIP21/CJ1W-EIP21) when available.

Fix this in Cj2m Cpu35 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2023-38744 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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