No exploitation reported

CVE-2020-5666

No exploitation reported by the sources we read.

Published2020-11-16
WeaknessCWE-400

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC

2020-11-1601:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-5666?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-5666?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Mitsubishielectric melsec iq-r00 firmwareversion to verify

Branch	Affected	Fixed in	Source
19.x	≥ 05, ≤ 19	no fix published	NVD

Mitsubishielectric melsec iq-r01 firmwareversion to verify

Branch	Affected	Fixed in	Source
19.x	≥ 05, ≤ 19	no fix published	NVD

Mitsubishielectric melsec iq-r02 firmwareversion to verify

Branch	Affected	Fixed in	Source
19.x	≥ 05, ≤ 19	no fix published	NVD

5 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

ICSA-20-317-01 CISA2 known affected
Mitsubishi Electric MELSEC iQ-R Series
MELSEC iQ-R series CPU module products R04/08/16/32/120(EN) CPU: Firmware versions from 35 to 51 · MELSEC iQ-R series CPU module products R00/01/02 CPU: Firmware versions from 05 to 19

Full record on NVD

Fix

Mitigation from the vendor CISA ICSA-20-317-01 · 2 productsR00/01/02CPU: firmware Versions 20 or later
Mitigation from the vendor CISA ICSA-20-317-01 · 2 productsR04/08/16/32/120(EN)CPU: firmware Versions 52 or later
Mitigation from the vendor CISA ICSA-20-317-01 · 2 productsIf the web server function is not needed, change the setting for "To Use or Not to Use Web Server” to “Not Use.”
Mitigation from the vendor CISA ICSA-20-317-01 · 2 productsUse a firewall or virtual private network (VPN), etc., to prevent unauthorized access when Internet access is required.
Mitigation from the vendor CISA ICSA-20-317-01 · 2 productsUse within a trusted LAN and block access from untrusted networks and hosts through firewall.
Mitigation from the vendor CISA ICSA-20-317-01 · 2 productsFor more information about this vulnerability and the associated mitigations, please see the vulnerability information on the Mitsubishi website.

Advisories and patches

www.mitsubishielectric.comMitigation · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.17.5read 2026-10-23
NVDCVSS 2.07.1read 2026-10-23
NVDweakness (CWE)CWE-400read 2026-10-23
FIRST EPSSEPSS score8.8 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2020-11-16
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2020-5666?

Is CVE-2020-5666 actively exploited?

Active exploitation of CVE-2020-5666 has not been confirmed. Its EPSS score was 8.8% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-5666?

CVE-2020-5666 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Hear about the next vulnerability in your software

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

Get alerts for this product CISA KEV additions, October 2026 Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Following what attackers exploit right now? The CISA KEV additions of the month, with their patch deadlines.
Running this software? Vulnerability monitoring alerts you to new vulnerabilities in your products.

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database