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Melsec Iq F Fx5 Enet\/ip FirmwareOperating system · Mitsubishielectric

CVE-2026-1876

HIGH · 7.5 CVSS v3.1 Published 2026-03-03
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
Improper Resource Shutdown or Release vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series FX5-ENET/IP Ethernet Module FX5-ENET/IP all versions 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 a resource exhaustion vulnerability in the MELSEC iQ-F Series FX5-ENET/IP Ethernet module. An unauthenticated remote attacker can cause a denial-of-service condition by continuously sending UDP packets to the affected device, which fails to properly manage resources under sustained UDP traffic. The device requires a manual system reset to recover.

MitigationIf vendor firmware updates are unavailable, implement network-level mitigations such as firewall rules or VLAN segmentation to restrict UDP traffic to the affected module from untrusted sources, and consider intrusion detection to alert on anomalous traffic patterns.

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 Enet\/ip 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 FX5-ENET/IP module presence
    Locate the physical Mitsubishi Electric FX5-ENET/IP Ethernet module attached to the FX5 PLC system, or check the PLC hardware configuration in GX Works3 software under the module list
    Affected if The FX5-ENET/IP module is installed in the system
  2. Confirm firmware version
    In GX Works3, navigate to the module's [Unit Information] or use the device's web interface (if enabled) to read the firmware version under the Ethernet module settings
    Affected if Any firmware version is reported (all versions are affected)
  3. Check UDP network exposure
    From a network scanner or by reviewing firewall rules, verify whether UDP ports on the FX5-ENET/IP module are reachable from untrusted network segments. Default UDP port is 2222 for EtherNet/IP but check actual configuration
    Affected if The module's UDP ports are accessible from untrusted/broadcast domains without filtering
  4. Review UDP traffic patterns
    Use a network packet capture (Wireshark, tcpdump) or industrial network monitoring tool to observe incoming UDP packet rate to the module's IP address
    Affected if Sustained high-volume UDP traffic is being received by the module
  5. Check for resource exhaustion symptoms
    In GX Works3 or via the module's diagnostics, monitor for indicators such as communication timeouts, inability to respond to new requests, or abnormal CPU/communication status indicators
    Affected if The module exhibits communication failures, hangs, or requires manual reset to restore operation

The environment is affected if a Mitsubishi Electric FX5-ENET/IP module with any firmware version is present and its UDP interfaces are reachable from untrusted network sources, exposing it to potential resource exhaustion from sustained UDP traffic.

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

If vendor firmware updates are unavailable, implement network-level mitigations such as firewall rules or VLAN segmentation to restrict UDP traffic to the affected module from untrusted sources, and consider intrusion detection to alert on anomalous traffic patterns.

Fix this in Melsec Iq F Fx5 Enet\/ip Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2026-1876 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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