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AUSCERT External Security Bulletin Redistribution
Advisory (icsa-20-317-01) Mitsubishi Electric MELSEC iQ-R Series
13 November 2020
AusCERT Security Bulletin Summary
Product: Mitsubishi Electric MELSEC iQ-R Series
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2020-5666
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ICS Advisory (ICSA-20-317-01)
Mitsubishi Electric MELSEC iQ-R Series
Original release date: November 12, 2020
All information products included in https://us-cert.cisa.gov/ics are
provided"as is" for informational purposes only. The Department of Homeland
Security (DHS) does not provide any warranties of any kind regarding any
information contained within. DHS does not endorse any commercial product or
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product is governed by the Traffic Light Protocol (TLP) marking in the header.
For more information about TLP, see https://us-cert.cisa.gov/tlp/ .
1. EXECUTIVE SUMMARY
o CVSS v3 6.8
o ATTENTION: Exploitable remotely
o Vendor: Mitsubishi Electric
o Equipment: MELSEC iQ-R series
o Vulnerability: Uncontrolled Resource Consumption
2. RISK EVALUATION
Successful exploitation of this vulnerability could cause a denial-of-service
condition for the affected products.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
Mitsubishi Electric reports the vulnerability affects the following MELSEC iQ-R
series CPU module products:
o R00/01/02 CPU Firmware versions from 05 to 19
o R04/08/16/32/120(EN) CPU Firmware versions from 35 to 51
3.2 VULNERABILITY OVERVIEW
3.2.1 UNCONTROLLED RESOURCE CONSUMPTION CWE-400
A denial-of-service vulnerability due to uncontrolled resource consumption
exists in MELSEC iQ-R series CPU modules. This vulnerability does not affect
products when the "To Use or Not to Use Web Server" parameter of CPU modules is
set to "Not Use." The default setting is "Not Use."
CVE-2020-5666 has been assigned to this vulnerability. A CVSS v3 base score of
6.8 has been calculated; the CVSS vector string is ( AV:N/AC:H/PR:N/UI:N/S:C/
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Japan
Xiaofei.Zhang, a researcher from China, reported this vulnerability to
Mitsubishi Electric has issued the following firmware versions to address this
o R00/01/02CPU firmware Versions 20 or later
o R04/08/16/32/120(EN)CPU firmware Versions 52 or later
Mitsubishi Electric also recommends the following practices:
o If the web server function is not needed, change the setting for "To Use or
Not to Use Web Server" to "Not Use."
o Use a firewall or virtual private network (VPN), etc., to prevent
unauthorized access when Internet access is required.
o Use within a trusted LAN and block access from untrusted networks and hosts
For more information about this vulnerability and the associated mitigations,
please see the vulnerability information on the Mitsubishi website .
CISA recommends users take defensive measures to minimize the risk of
exploitation of this vulnerability. Specifically, users should:
o Minimize network exposure for all control system devices and/or systems,
and ensure that they are not accessible from the Internet .
o Locate control system networks and remote devices behind firewalls, and
isolate them from the business network.
o When remote access is required, use secure methods, such as Virtual Private
Networks (VPNs), recognizing that VPNs may have vulnerabilities and should
be updated to the most current version available. Also recognize that VPN
is only as secure as the connected devices.
CISA reminds organizations to perform proper impact analysis and risk
assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices
on the ICS webpage on us-cert.cisa.gov . Several recommended practices are
available for reading and download, including Improving Industrial Control
Systems Cybersecurity with Defense-in-Depth Strategies .
Additional mitigation guidance and recommended practices are publicly available
on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation
Organizations observing any suspected malicious activity should follow their
established internal procedures and report their findings to CISA for tracking
and correlation against other incidents.
No known public exploits specifically target this vulnerability. High skill
level is needed to exploit.
For any questions related to this report, please contact the CISA at:
Toll Free: 1-888-282-0870
CISA continuously strives to improve its products and services. You can help by
choosing one of the links below to provide feedback about this product.
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