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Melsec Iq F Fx5 Eip FirmwareOperating system · Mitsubishielectric

CVE-2026-1874

HIGH · 7.5 CVSS v3.1 Published 2026-03-03
Fix available
A fix is available. Upgrade to after 1.106 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
Always-Incorrect Control Flow Implementation vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series FX5-ENET/IP Ethernet Module FX5-ENET/IP versions 1.106 and prior and Mitsubishi Electric Corporation MELSEC iQ-F Series FX5-EIP EtherNet/IP Module FX5-EIP versions 1.000 and prior allows a remote attacker to cause a denial-of-service (DoS) condition on the products by continuously sending UDP packets to the products. A system reset of the product is required for recovery.

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

This is an Always-Incorrect Control Flow Implementation vulnerability in Mitsubishi Electric's MELSEC iQ-F Series Ethernet modules (FX5-ENET/IP and FX5-EIP). A remote attacker can cause a persistent denial-of-service condition by continuously sending specially crafted UDP packets to the affected devices, which causes the modules to become unresponsive and requires a manual system reset for recovery.

MitigationNetwork segmentation and firewall rules should be implemented to restrict UDP traffic to the affected modules from untrusted sources. Once Mitsubishi Electric releases patched firmware versions, immediate application is recommended along with testing in a staging environment before production deployment.

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 F Fx5 Eip FirmwareOperating system
Affected:<= 1.000
Melsec Iq F Fx5 Enet\/ip FirmwareOperating system
Affected:<= 1.106

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 the installed Ethernet module model
    Locate the physical module on the MELSEC iQ-F Series PLC rack or check the system configuration in GX Works3. Confirm whether the module is FX5-EIP (Ethernet/IP) or FX5-ENET/IP.
    Affected if The module is either FX5-EIP or FX5-ENET/IP.
  2. Determine the firmware version of the Ethernet module
    Access the module properties via GX Works3 (MELSEC iQ-F programming software) or through the module's built-in web server if enabled. Record the firmware version number displayed.
    Affected if The firmware version is 1.000 or lower for FX5-EIP, or 1.106 or lower for FX5-ENET/IP.
  3. Verify network exposure of the affected module
    Review network firewall rules and segment configurations to determine whether the Ethernet module is accessible from untrusted network segments. Check if UDP ports used by the Ethernet/IP or ENET/IP protocol are exposed to external or less-trusted networks.
    Affected if The module UDP ports are reachable from untrusted network sources or the internet.
  4. Check for signs of module unresponsiveness
    Monitor PLC communication status in GX Works3 or observe whether the Ethernet module stops responding to network requests. Attempt a ping or protocol-specific query to the module IP address.
    Affected if The module has become unresponsive or fails to respond to legitimate network queries after receiving crafted UDP packets.

A user is affected if they have an FX5-EIP (firmware <=1.000) or FX5-ENET/IP (firmware <=1.106) module with its UDP interfaces exposed to untrusted networks, or if the module has already become unresponsive.

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.

dbcve · scoped
Upgrade available Upgrade to a release after 1.106
Interim mitigation

Network segmentation and firewall rules should be implemented to restrict UDP traffic to the affected modules from untrusted sources. Once Mitsubishi Electric releases patched firmware versions, immediate application is recommended along with testing in a staging environment before production deployment.

Recommended fix Moderate confidence

FX5-ENET/IP version 1.107 or later; FX5-EIP version 1.001 or later

  1. Identify the specific model of the affected device (FX5-ENET/IP or FX5-EIP)
  2. Locate the Mitsubishi Electric download page for MELSEC iQ-F series firmware updates
  3. Download the latest firmware version from the official Mitsubishi Electric support website
  4. Consult the device manual for firmware update instructions specific to your model
  5. Ensure the firmware update is performed in a controlled environment with stable power
  6. After updating, verify the firmware version has been successfully applied
  7. Test normal network operations to confirm the device functions correctly after the update
Caveat Firmware updates should be tested in a non-production environment first; ensure backup of device configuration before updating; some legacy communication settings may need reconfiguration after firmware upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Melsec Iq F Fx5 Eip Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,120
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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-2026-1874 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