What is CVE-2020-5666?

CVE-2020-5666 is a high-severity vulnerability in Mitsubishielectric Melsec Iq-R00, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2020-11-16.

How severe is CVE-2020-5666?

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

Resource exhaustion in Mitsubishielectric Melsec Iq-R00

CVE-2020-5666

Uncontrolled resource consumption vulnerability in MELSEC iQ-R Series CPU Modules (R00/01/02CPU Firmware versions from '05' to '19' and R04/08/16/32/120(EN)CPU Firmware versions from '35' to '51') allows a remote attacker to cause an error in a CPU unit via a specially crafted HTTP packet, which may lead to a denial-of-service (DoS) condition in execution of the program and its communication.

Vulnerability class: DoS (Denial of Service)

Published 2020-11-16 · 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: 0.088 (95.0th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 95th percentile — 95.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.088 · newest: 0.088 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2020-015_en.pdf (Mitigation, Vendor Advisory)
jvn.jp/jp/JVN44764844/index.html (Third Party Advisory)
jvn.jp/en/jp/JVN44764844/index.html (Third Party Advisory)
us-cert.cisa.gov/ics/advisories/icsa-20-317-01 (US Government Resource, Third Party Advisory)

Frequently asked questions

What is CVE-2020-5666?: CVE-2020-5666 is a high-severity vulnerability in Mitsubishielectric Melsec Iq-R00, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2020-11-16.
How severe is CVE-2020-5666?: High severity. CVSS v3 base score is 7.5 out of 10.