CVE-2021-20600Network attack vector

Startup denial of service via packet flood

Published Oct 8, 2021 · Updated Aug 3, 2024

Uncontrolled resource consumption in Mitsubishi Electric R12CCPU-V firmware 16 and earlier allows remote attackers to prevent startup. During the READY-LED blinking startup phase, network processing consumes resources under a short packet burst until a system WDT error occurs. No authentication or user interaction is required, but the condition exists only during startup; the module then fails to start and requires a system reset.

CVSS severity6.8
Medium
EPSS probability2.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Mitsubishi Electric R12CCPU-V firmware 16 and earlier allows remote attackers to prevent startup. During the READY-LED blinking startup phase, network processing consumes resources under a short packet burst until a system WDT error occurs. No authentication or user interaction is required, but the condition exists only during startup; the module then fails to start and requires a system reset.

The record

CVE
CVE-2021-20600
Published
Oct 8, 2021
Updated
Aug 3, 2024
Vendor
Mitsubishi Electric Corporation
Product
MELSEC iQ-R C Controller Module
Classifications
CWE-400, T0814
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 8, 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=Mitsubishi Electric MELSEC iQ-R series C Controller Module R12CCPU-V Firmware Versions "16" and prior

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mitsubishi Electric Corporation · MELSEC iQ-R C Controller Moduleversion=Mitsubishi Electric MELSEC iQ-R series C Controller Module R12CCPU-V Firmware Versions "16" and prior

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
6.8Mitsubishi Electric CorporationCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
7.1NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:C
6.8JPCERT/CCCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/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.

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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-400Uncontrolled Resource Consumption
T0814Denial 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

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Your stack

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