What is CVE-2021-20591?

CVE-2021-20591 is a high-severity vulnerability in Mitsubishielectric R00cpu, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2021-06-11.

How severe is CVE-2021-20591?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Mitsubishielectric R00cpu

CVE-2021-20591

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.

Vulnerability class: DoS (Denial of Service)

Published 2021-06-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.015 (73.2th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 73rd percentile — 73.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.015 · newest: 0.015 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2021-003_en.pdf (Vendor Advisory)
jvn.jp/vu/JVNVU98060539/index.html (Third Party Advisory)

Frequently asked questions

What is CVE-2021-20591?: CVE-2021-20591 is a high-severity vulnerability in Mitsubishielectric R00cpu, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2021-06-11.
How severe is CVE-2021-20591?: High severity. CVSS v3 base score is 7.5 out of 10.