Mitsubishi Electric MELSEC-F Series

1. EXECUTIVE SUMMARY

• CVSS v3 7.5
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Mitsubishi Electric
• Equipment: MELSEC-F Series
• Vulnerability: Improper Initialization

2. RISK EVALUATION

Successful exploitation of this vulnerability may cause a denial-of-service condition in the affected product.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following versions of MELSEC-F Series with FX3U-ENET, an Ethernet-Internet block, are affected:

• FX3U-ENET: Firmware Version 1.16 and prior
• FX3U-ENET-L: Firmware Version 1.16 and prior
• FX3U-ENET-P502: Firmware Version 1.16 and prior

3.2 VULNERABILITY OVERVIEW

3.2.1    IMPROPER INITIALIZATION CWE-665

An attacker could send a specially crafted packet that could create a denial-of-service condition in the communication function of the product. A system reset is required for recovery.

CVE-2021-20613 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

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

3.4 RESEARCHER

Mitsubishi Electric reported this vulnerability to CISA.

4. MITIGATIONS

Mitsubishi Electric corrected this vulnerability in the following products and versions, as follows:

• FX3U-ENET: Firmware Version 1.17 or later
• FX3U-ENET-L: Firmware Version 1.17 or later
• FX3U-ENET-P502: Firmware Version 1.17 or later

Mitsubishi Electric also recommends users take the following mitigation measures to minimize the risk of exploiting this vulnerability:

• Use a firewall, VPN, or other barrier to prevent unauthorized access when Internet access is required.
• Use within a LAN and block access from untrusted networks and hosts through firewalls.

For specific update instructions and additional details see the Mitsubishi Electric advisory.

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.

• Mitsubishi Electric