CVE-2021-20613Network attack vector

Unauthenticated communications outage via crafted packets

Published Jan 14, 2022 · Updated Aug 3, 2024

Improper initialization in Mitsubishi Electric MELSEC-F Ethernet blocks through firmware 1.16 lets remote attackers halt communications. Public advisories disclose only that crafted packets reach an improperly initialized communication function; no lower-level code locus or operation is published. Unauthenticated network access is sufficient, the PLC retains control, and communications remain unavailable until a system reset.

CVSS severity7.5
High
EPSS probability3.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper initialization in Mitsubishi Electric MELSEC-F Ethernet blocks through firmware 1.16 lets remote attackers halt communications. Public advisories disclose only that crafted packets reach an improperly initialized communication function; no lower-level code locus or operation is published. Unauthenticated network access is sufficient, the PLC retains control, and communications remain unavailable until a system reset.

The record

CVE
CVE-2021-20613
Published
Jan 14, 2022
Updated
Aug 3, 2024
Vendor
Mitsubishi Electric Corporation
Product
MELSEC-F Series Ethernet Interface Block
Classifications
CWE-665, T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 14, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Firmware version 1.16 and prior

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mitsubishi Electric Corporation · MELSEC-F Series Ethernet Interface Blockversion=Firmware version 1.16 and prior

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.8NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-665Improper Initialization
T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo