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AUSCERT External Security Bulletin Redistribution
Advisory (icsa-21-021-04) Mitsubishi Electric MELFA
22 January 2021
AusCERT Security Bulletin Summary
Product: Mitsubishi Electric MELFA
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2021-20586
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ICS Advisory (ICSA-21-021-04)
Mitsubishi Electric MELFA
Original release date: January 21, 2021
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1. EXECUTIVE SUMMARY
o CVSS v3 7.5
o ATTENTION: Exploitable remotely/low skill level to exploit
o Vendor: Mitsubishi Electric
o Equipment: MELFA FR, MELFA CR, MELFA ASSISTA
o Vulnerability: Uncontrolled Resource Consumption
2. RISK EVALUATION
Successful exploitation of this vulnerability could cause a denial-of-service
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
Mitsubishi Electric reports the vulnerability affects the following MELFA robot
o MELFA FR Series
RV-#FR$%\-R-@ R16RTCPU + CR800-#V$R
RH-#FRH$&\-R-@ R16RTCPU + CR800-#HR
RH-#FRHR$&\-R-@ R16RTCPU + CR800-#HRR
RV-#FR$%\-Q-@ Q172DSRCPU + CR800-#V$Q
RH-#FRH$&\-Q-@ Q172DSRCPU + CR800-#HQ
RH-#FRHR$&\-Q-@ Q172DSRCPU + CR800-#HRQ
o MELFA CR Series
o MELFA ASSISTA: RV-5AS-D-@ CR800-05VD
3.2 VULNERABILITY OVERVIEW
3.2.1 UNCONTROLLED RESOURCE CONSUMPTION CWE-400
These robot controllers may allow an attacker to cause a denial-of-service of
the execution of the robot program and the Ethernet communication by sending
many packets in a burst over a short period.
CVE-2021-20586 has been assigned to this vulnerability. A CVSS v3 base score of
7.5 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:N/UI:N/S:U/
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Japan
Industrial Control Security Laboratory of Qi An Xin Group, Inc., reported this
vulnerability to Mitsubishi Electric.
Mitsubishi Electric recommends users take the following mitigation measures to
minimize the risk of exploiting this vulnerability:
o Use a firewall or virtual private network (VPN), etc. to prevent
unauthorized access when Internet access is required.
o Use within a LAN and block access from untrusted networks and hosts through
Please refer to the Mitsubishi Electric website for details on how to check
Additional information about the vulnerabilities or Mitsubishi Electric's
compensating control is available by contacting a Mitsubishi Electric
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.
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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