CVE-2021-20600

highpriority · track · 25EPSS 0.024 · 84 %ileEUUS
grimoire priorityP2 · Scheduled
Exploitable?
—
no known exploitation
Likely / severe?
2.38% (84th) EPSS
CVSS 7.1 · high
Is it mine?
4 products
Check your exposure
Who says so?
4 sources
cnnvd · enisa_euvd · cisa_csaf_ot · nvd

EPSS · scored 2026-10-27

Uncontrolled resource consumption in Mitsubishi Electric MELSEC iQ-R series C Controller Module R12CCPU-V Firmware Versions "16" and prior allows a remote unauthenticated attacker to cause a denial-of-service (DoS) condition by sending a large number of packets in a short time while the module starting up. System reset is required for recovery.

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

No vendor fix yet; a mitigation is available.

  • MitigationR12CCPU-Vcisa_csaf_ot

    If a System WDT error occurs at start up, there is a possibility the C Controller Module has been attacked. In this case, disconnect the LAN cable of the module and restart. After confirming the module has started normally, make a LAN connection.

02

cvss

Technical severity, 0–10. One row per scoring source.

7.1
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5.4–7.1

v2.07.1highAV:N/AC:M/Au:N/C:N/I:N/A:Cprimary · NVD / NIST USexploitability 8.6 · impact 6.9
v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:Hprimary · NVD / NIST USexploitability 2.2 · impact 3.6
v3.06.8mediumCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:Hsecondary · CISA US
v3.15.4mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:Usecondary · CVSS-BT (t0sche)
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-400USprimaryCWE-400US
04

affected products (4)

Products and version ranges known to be affected.

05

advisories (1)

Vendor and ecosystem advisories describing this.

  • ICSA-21-280-04Mitsubishi Electric MELSEC iQ-R Series C Controller Module (Update B)2021-10-07icsa · cisa_csaf_otUS

    Successful exploitation of this vulnerability could prevent the module from starting up. If successfully exploited, a system reset would be required for recovery.

06

also known as (3)

Other names and identifiers for this entity.

07

sources

Which sources assert this record, and when.

cnnvdenisa_euvdcisa_csaf_otnvdNVDCVE.orgMITRE
published 2021-10-08modified 2026-06-17
09

references (12)

External citations — patches, advisories, analysis.

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