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AUSCERT External Security Bulletin Redistribution
ESB-2021.2464
Advisory (icsa-21-201-01) Mitsubishi Electric MELSEC-F Series
21 July 2021
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AusCERT Security Bulletin Summary
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Product: Mitsubishi Electric MELSEC-F Series
Publisher: ICS-CERT
Operating System: Network Appliance
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2021-20596
Original Bulletin:
https://us-cert.cisa.gov/ics/advisories/icsa-21-201-01
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ICS Advisory (ICSA-21-201-01)
Mitsubishi Electric MELSEC-F Series
Original release date: July 20, 2021
Legal Notice
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 service,
referenced in this product or otherwise. Further dissemination of this 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 7.5
o ATTENTION: Exploitable remotely/low attack complexity
o Vendor: Mitsubishi Electric
o Equipment: MELSEC-F Series
o Vulnerability: NULL Pointer Dereference
2. RISK EVALUATION
Successful exploitation of this vulnerability may cause a denial-of-service
condition in communication with the product. System reset may be required for
recovery.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
Mitsubishi Electric reports this vulnerability exists in the following MELSEC-F
series Ethernet interface block:
o FX3U-ENET: Firmware Version 1.14 and prior
o FX3U-ENET-L: Firmware Version 1.14 and prior
o FX3U-ENET-P502: Firmware Version 1.14 and prior
3.2 VULNERABILITY OVERVIEW
3.2.1 NULL POINTER DEREFERENCE CWE-476
Malicious attacker may cause a denial-of-service condition in communication
with the product by sending specially crafted packets.
CVE-2021-20596 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/
C:N/I:N/A:H ).
3.3 BACKGROUND
o CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: Japan
3.4 RESEARCHER
Mitsubishi Electric reported this vulnerability to CISA.
4. MITIGATIONS
Mitsubishi Electric Corporation recommends using the newest version of firmware
possible. The fixed products and versions are as follows:
o FX3U-ENET:Firmware Version 1.16 or later
o FX3U-ENET-L:Firmware Version 1.16 or later
o FX3U-ENET-P502:Firmware Version 1.16 or later
To minimize the risk of exploiting this vulnerability, Mitsubishi Electric
Corporation recommends users take the following mitigations:
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
firewalls.
Please refer to the Mitsubishi Electric advisory for further details.
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
Strategies .
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:
Email: CISAservicedesk@cisa.dhs.gov
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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