Successful exploitation of this vulnerability may prevent the FTP client from connecting to the FTP server on MELSEC-Q Series and MELSEC-L Series CPU module.
Only FTP server function is affected by this vulnerability.
The following versions of MELSEC-Q Series and MELSEC-L Series CPU modules are affected:
A remote attacker can cause the FTP service to enter a denial-of-service condition dependent on the timing at which a remote attacker connects to the FTP server on the above CPU modules.
Tri Quach of Amazon’s Customer Fulfillment Technology Security (CFTS) group reported this vulnerability to CISA.
Mitsubishi Electric has produced a new version of the firmware. Additional information about this vulnerability or Mitsubishi Electric's compensating control is available by contacting a local Mitsubishi Electric representative, which can be found at the following location:
Mitsubishi Electric strongly recommends that users should operate the affected device behind a firewall.
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. Specifically, users should:
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.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.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:
Toll Free: 1-888-282-0870
For industrial control systems cybersecurity information: https://www.us-cert.gov/ics
or incident reporting: https://www.us-cert.gov/report
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