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AUSCERT External Security Bulletin Redistribution
Advisory (icsa-21-250-01) Mitsubishi Electric MELSEC iQ-R Series
8 September 2021
AusCERT Security Bulletin Summary
Product: Mitsubishi Electric MELSEC iQ-R Series
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Access Confidential Data -- Remote/Unauthenticated
Reduced Security -- Remote/Unauthenticated
CVE Names: CVE-2021-20598 CVE-2021-20597 CVE-2021-20594
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ICS Advisory (ICSA-21-250-01)
Mitsubishi Electric MELSEC iQ-R Series
Original release date: September 07, 2021
All information products included in https://us-cert.cisa.gov/ics are provided
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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 7.4
o ATTENTION: Exploitable remotely
o Vendor: Mitsubishi Electric Corporation
o Equipment: MELSEC iQ-R Series CPU Module
o Vulnerabilities: Exposure of Sensitive Information to an Unauthorized
Actor, Insufficiently Protected Credentials, Overly Restrictive Account
2. RISK EVALUATION
Successful exploitation of these vulnerabilities could allow a remote attacker
unauthorized access to legitimate usernames, CPU module access, or the ability
to deny access to legitimate users.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
Mitsubishi Electric reports these vulnerabilities affect the following MELSEC
o R08/16/32/120SFCPU: All versions
o R08/16/32/120PSFCPU: All versions
3.2 VULNERABILITY OVERVIEW
3.2.1 EXPOSURE OF SENSITIVE INFORMATION TO AN UNAUTHORIZED ACTOR CWE-200
A remote attacker can leverage a brute-force attack to acquire legitimate
usernames registered in the module.
CVE-2021-20594 has been assigned to this vulnerability. A CVSS v3 base score of
5.9 has been calculated; the CVSS vector string is ( AV:N/AC:H/PR:N/UI:N/S:U/
3.2.2 INSUFFICIENTLY PROTECTED CREDENTIALS CWE-522
A remote attacker could obtain unprotected credentials by sniffing network
CVE-2021-20597 has been assigned to this vulnerability. A CVSS v3 base score of
7.4 has been calculated; the CVSS vector string is ( AV:N/AC:H/PR:N/UI:N/S:U/
3.2.3 OVERLY RESTRICTIVE ACCOUNT LOCKOUT MECHANISM CWE-645
A remote attacker could lock out a legitimate user by continually attempting to
login with a known username and incorrect passwords.
CVE-2021-20598 has been assigned to this vulnerability. A CVSS v3 base score of
3.7 has been calculated; the CVSS vector string is ( AV:N/AC:H/PR:N/UI:N/S:U/
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Japan
Ivan Speziale of Nozomi Networks Labs reported these vulnerabilities to CISA.
Mitsubishi Electric plans to release fixed versions of the firmware for
CVE-2021-20594 and CVE-2021-20597 in the future.
Mitsubishi Electric recommends users take the following mitigation measures to
minimize the risk of exploiting these vulnerabilities:
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
o Use the IP filter function* to restrict the accessible IP addresses.
o Register user information or change the password via USB. If you have
already registered user information or changed the user's password via the
network, change the password once via USB. This mitigation is applicable to
* MELSEC iQ-R Ethernet User's Manual (Application) 1.13 Security "IP filter"
Additional information about these 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 these vulnerabilities. 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.
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.
CISA also recommends users take the following measures to protect themselves
from social engineering attacks:
o Do not click web links or open unsolicited attachments in email messages.
o Refer to Recognizing and Avoiding Email Scams for more information on
avoiding email scams.
o Refer to Avoiding Social Engineering and Phishing Attacks for more
information on social engineering attacks.
No known public exploits specifically target these vulnerabilities. These
vulnerabilities have a high attack complexity.
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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