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Fencer Vulns
high 7.5

CVE-2021-20591 json

Uncontrolled Resource Consumption vulnerability in Mitsubishi Electric MELSEC iQ-R series CPU modules (R00/01/02CPU all versions, R04/08/16…

published 2021-06-11 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-8009

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 74%
public exploits
0
none known

Summary

Uncontrolled Resource Consumption vulnerability in Mitsubishi Electric MELSEC iQ-R series CPU modules (R00/01/02CPU all versions, R04/08/16/32/120(EN)CPU all versions, R08/16/32/120SFCPU all versions, R08/16/32/120PCPU all versions, R08/16/32/120PSFCPU all versions) allows a remote unauthenticated attacker to prevent legitimate clients from connecting to the MELSOFT transmission port (TCP/IP) by not closing a connection properly, which may lead to a denial of service (DoS) condition.

Vendor advisories

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

cisa ICSA-21-147-05 updated cvss 5.3

Mitsubishi Electric MELSEC iQ-R Series

  • Mitsubishi Electric R00/01/02CPU Mitsubishi Electric R04/08/16/32/120(EN)CPU Mitsubishi Electric R08/16/32/120PCPU Mitsubishi Electric R08/16/32/120PSFCPU Mitsubishi Electric R08/16/32/120SFCPU
    affected: mitigation “Use a firewall, a virtual private network (VPN), etc., to prevent unauthorized access when Internet access is required.” 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

1.50% chance of exploitation in the next 30 days, higher than 74% 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 iQ-R series CPU modules

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

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.