Mitsubishi Electric GOT and Tension Controller (Update A)

1. EXECUTIVE SUMMARY

• CVSS v3 5.9
• ATTENTION: Exploitable remotely
• Vendor: Mitsubishi Electric
• Equipment: GOT and Tension Controller
• Vulnerability: Buffer Access with Incorrect Length Value

2. UPDATE INFORMATION

This updated advisory is a follow-up to the original advisory titled ICSA-21-131-02 Mitsubishi Electric GOT and Tension Controller that was published May 11, 2021, to the ICS webpage on www.cisa.gov/uscert/ics.

3. RISK EVALUATION

Successful exploitation of this vulnerability may be able to stop the communication function of the products, requiring a reset to regain functionality.

4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

Mitsubishi Electric reports the vulnerability affects the MODBUS/TCP slave communication function of the following devices:

• GOT2000 series
  • GT27 model: Versions 01.19.000 - 01.38.000
  • GT25 model: Versions 01.19.000 - 01.38.000
  • GT23 model: Versions 01.19.000 - 01.38.000
  • GT21 model: Versions 01.21.000 - 01.39.000
• GOT SIMPLE series
  • GS21 model: Versions 01.21.000 - 01.39.000
• GT SoftGOT2000: Versions 1.170C - 1.250L
• LE7-40GU-L Screen package data for MODBUS/TCP: v1.00

Please see Mitsubishi Electric report number 2021-002 to learn how to check which version is in use.

4.2 VULNERABILITY OVERVIEW

4.2.1    BUFFER ACCESS WITH INCORRECT LENGTH VALUE CWE-805

An attacker could exploit this vulnerability to cause a denial-of-service condition in the MODBUS/TCP server communication function of GOT2000 series, GOT SIMPLE series, SoftGOT2000 and Tension Controller.

CVE-2021-20589 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/C:N/I:N/A:H).

4.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Japan

4.4 RESEARCHER

Parul Sindhwad and Dr. Faruk Kazi of COE-CNDS Lab, VJTI, Mumbai, India reported this vulnerability to Mitsubishi Electric.

5. MITIGATIONS

Mitsubishi Electric has created the following versions to address this vulnerability:

• GOT2000 series: GT27 model, GT25 model, and GT23 model: update to 01.39.000 or later.
• GOT2000 series: GT21 model: update to 01.40.000 or later.
• GOT SIMPLE series GS21 model: update to 01.40.000 or later.
• GT SoftGOT2000: update to 1.255R or later.

--------- Begin Update A Part 1 of 1 ---------

• LE7-40GU-L Screen package data for MODBUS/TCP: update to v1.01 or later.

--------- End Update A Part 1 of 1 ---------

Please refer to the Mitsubishi Electric website for detailed update procedures.

Mitsubishi Electric recommends the following mitigations until users can update to safer versions:

• When connecting the product to the Internet, use a firewall or virtual private network (VPN) to prevent unauthorized access.
• Use it within the LAN and make it inaccessible from untrusted networks and hosts.
• Install antivirus software on a computer that can access the product.

CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. 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 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 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. High attack complexity.