CVE-2021-20608Network attack vector

Application crash via inconsistent PLC file lengths

Published Dec 17, 2021 · Updated Aug 3, 2024

Improper length handling in Mitsubishi Electric GX Works2 1.606G and earlier allows remote attackers to crash the application. GX Works2 mishandles inconsistent length metadata when it reads a PLC program file that crafted packets have tampered with. Exploitation requires unauthenticated network access to the PLC and a user to read the altered file; the PLC itself remains operational.

CVSS severity5.3
Medium
EPSS probability2.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper length handling in Mitsubishi Electric GX Works2 1.606G and earlier allows remote attackers to crash the application. GX Works2 mishandles inconsistent length metadata when it reads a PLC program file that crafted packets have tampered with. Exploitation requires unauthenticated network access to the PLC and a user to read the altered file; the PLC itself remains operational.

The record

CVE
CVE-2021-20608
Published
Dec 17, 2021
Updated
Aug 3, 2024
Vendor
Mitsubishi Electric Corporation
Product
MELSOFT GX Works2
Classifications
CWE-130, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 17, 2021CVE 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

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Is a vulnerable build present?

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

  1. Affected versionversion=versions 1.606G and prior

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mitsubishi Electric Corporation · MELSOFT GX Works2version=versions 1.606G and prior

Published CVSS scores

5.3Mitsubishi Electric CorporationCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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-130Improper Handling of Length Parameter Inconsistency
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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