Improper initialization vulnerability in MELSEC-F series FX3U-ENET Firmware version 1.16 and prior, FX3U-ENET-L Firmware version 1.16 and p…

published 2022-01-14 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-8031

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 3.8%; EPSS 3.8% chance of exploitation in 30 days, percentile 90%
public exploits: 0; none known

Improper initialization vulnerability in MELSEC-F series FX3U-ENET Firmware version 1.16 and prior, FX3U-ENET-L Firmware version 1.16 and prior and FX3U-ENET-P502 Firmware version 1.16 and prior allows a remote unauthenticated attacker to cause a denial-of-service (DoS) condition in communication function of the product by sending specially crafted packets. Control by MELSEC-F series PLC is not affected by this vulnerability, but system reset is required for recovery.

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

cisa ICSA-22-013-07 updated 2022-01-13 cvss 7.5

Mitsubishi Electric MELSEC-F Series

Mitsubishi Electric FX3U-ENET <= 1.16 Mitsubishi Electric FX3U-ENET-L <= 1.16 Mitsubishi Electric FX3U-ENET-P502 <= 1.16
affected: vendor fix, mitigation “Mitsubishi Electric corrected this vulnerability in the following products and versions, as follows:” mitsubishielectric.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

3.82% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	7.8	AV:N/AC:L/Au:N/C:N/I:N/A:C

Affected products

n/a MELSEC-F series FX3U-ENET; MELSEC-F series FX3U-ENET-L; MELSEC-F series FX3U-ENET-P502

Classification

Weakness

CWE-665 Improper Initialization

References

mitsubishielectric.com /en/psirt/vulnerability/pdf/2021-024_en.pdf
vendor-advisory
jvn.jp /vu/JVNVU93268332/index.html
third-party-advisory, vdb-entry
cisa.gov /uscert/ics/advisories/icsa-22-013-07
third-party-advisory, us-government-resource

Sources

CVE List CVE-2021-20613
NVD CVE-2021-20613

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary