Mitsubishi Electric Corporation MELSEC iQ-F Series CPU Module

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1. EXECUTIVE SUMMARY CVSS v3 5.3 ATTENTION: Exploitable remotely/Low attack complexity Vendor: Mitsubishi Electric Corporation Equipment: MELSEC iQ-F Series CPU module Vulnerability: Improper Handling of Length Parameter Inconsistency
2. RISK EVALUATION Successful exploitation of this vulnerability could result in a remote attacker being able to delay the processing of the Web server function and prevent legitimate users from utilizing the Web server function by sending a specially crafted HTTP request.
3. TECHNICAL DETAILS 3.1 AFFECTED PRODUCTS The following versions of MELSEC iQ-F Series CPU module are affected: MELSEC iQ-F Series CPU module FX5U-32MT/ES: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-32MT/DS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-32MT/ESS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-32MT/DSS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-32MR/ES: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-32MR/DS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-64MT/ES: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-64MT/DS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-64MT/ESS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-64MT/DSS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-64MR/ES: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-64MR/DS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-80MT/ES: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-80MT/DS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-80MT/ESS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-80MT/DSS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-80MR/ES: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5U-80MR/DS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-32MT/D: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-32MT/DSS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-64MT/D: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-64MT/DSS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-96MT/D: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-96MT/DSS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-32MT/DS-TS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-32MT/DSS-TS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UC-32MR/DS-TS: Versions 1.060 and later MELSEC iQ-F Series CPU module FX5UJ-24MT/ES: All versions MELSEC iQ-F Series CPU module FX5UJ-24MT/DS: All versions MELSEC iQ-F Series CPU module FX5UJ-24MT/ESS: All versions MELSEC iQ-F Series CPU module FX5UJ-24MT/DSS: All versions MELSEC iQ-F Series CPU module FX5UJ-24MR/ES: All versions MELSEC iQ-F Series CPU module FX5UJ-24MR/DS: All versions MELSEC iQ-F Series CPU module FX5UJ-40MT/ES: All versions MELSEC iQ-F Series CPU module FX5UJ-40MT/DS: All versions MELSEC iQ-F Series CPU module FX5UJ-40MT/ESS: All versions MELSEC iQ-F Series CPU module FX5UJ-40MT/DSS: All versions MELSEC iQ-F Series CPU module FX5UJ-40MR/ES: All versions MELSEC iQ-F Series CPU module FX5UJ-40MR/DS: All versions MELSEC iQ-F Series CPU module FX5UJ-60MT/ES: All versions MELSEC iQ-F Series CPU module FX5UJ-60MT/DS: All versions MELSEC iQ-F Series CPU module FX5UJ-60MT/ESS: All versions MELSEC iQ-F Series CPU module FX5UJ-60MT/DSS: All versions MELSEC iQ-F Series CPU module FX5UJ-60MR/ES: All versions MELSEC iQ-F Series CPU module FX5UJ-60MR/DS: All versions MELSEC iQ-F Series CPU module FX5UJ-24MT/ES-A: All versions MELSEC iQ-F Series CPU module FX5UJ-24MR/ES-A: All versions MELSEC iQ-F Series CPU module FX5UJ-40MT/ES-A: All versions MELSEC iQ-F Series CPU module FX5UJ-40MR/ES-A: All versions MELSEC iQ-F Series CPU module FX5UJ-60MT/ES-A: All versions MELSEC iQ-F Series CPU module FX5UJ-60MR/ES-A: All versions MELSEC iQ-F Series CPU module FX5S-30MT/ES: All versions MELSEC iQ-F Series CPU module FX5S-30MT/DS: All versions MELSEC iQ-F Series CPU module FX5S-30MT/ESS: All versions MELSEC iQ-F Series CPU module FX5S-30MT/DSS: All versions MELSEC iQ-F Series CPU module FX5S-30MR/ES: All versions MELSEC iQ-F Series CPU module FX5S-30MR/DS: All versions MELSEC iQ-F Series CPU module FX5S-40MT/ES: All versions MELSEC iQ-F Series CPU module FX5S-40MT/DS: All versions MELSEC iQ-F Series CPU module FX5S-40MT/ESS: All versions MELSEC iQ-F Series CPU module FX5S-40MT/DSS: All versions MELSEC iQ-F Series CPU module FX5S-40MR/ES: All versions MELSEC iQ-F Series CPU module FX5S-40MR/DS: All versions MELSEC iQ-F Series CPU module FX5S-60MT/ES: All versions MELSEC iQ-F Series CPU module FX5S-60MT/DS: All versions MELSEC iQ-F Series CPU module FX5S-60MT/ESS: All versions MELSEC iQ-F Series CPU module FX5S-60MT/DSS: All versions MELSEC iQ-F Series CPU module FX5S-60MR/ES: All versions MELSEC iQ-F Series CPU module FX5S-60MR/DS: All versions MELSEC iQ-F Series CPU module FX5S-80MT/ES: All versions MELSEC iQ-F Series CPU module FX5S-80MT/ESS: All versions MELSEC iQ-F Series CPU module FX5S-80MR/ES: All versions 3.2 VULNERABILITY OVERVIEW 3.2.1 IMPROPER HANDLING OF LENGTH PARAMETER INCONSISTENCY CWE-130 A Denial-of-Service (DoS) vulnerability due to Improper Handling of Length Parameter Inconsistency exists in the Web server function of the MELSEC iQ-F Series CPU module. CVE-2025-5514 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L). 3.3 BACKGROUND CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing COUNTRIES/AREAS DEPLOYED: Worldwide COMPANY HEADQUARTERS LOCATION: Japan 3.4 RESEARCHER Thai Do, Minh Pham, Quan Le, and Loc Nguyen of OPSWAT Unit515 reported this vulnerability to Mitsubishi Electric Corporation. Mitsubishi Electric Corporation reported this vulnerability to CISA.
4. MITIGATIONS Mitsubishi Electric Corporation advises that there are no plans to release a fixed version. Mitsubishi Electric recommends users take the following mitigation measures to minimize the risk of exploiting this vulnerability: Use a firewall or virtual private network (VPN), etc. to prevent unauthorized access when Internet access is required. Use within a LAN and block access from untrusted networks and hosts through firewalls. Use IP filter function to block access from untrusted hosts. For details on the IP filter function, please refer to the manual for each product: “13.1 IP Filter Function” in the MELSEC iQ-F FX5 User’s Manual (Communication). Restrict physical access to the affected products and the LAN connected by them. Mitsubishi Electric Corporation recommends users contact their local Mitsubishi Electric representative with questions. For more information, see Mitsubishi Electric’s security advisory. CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability, such as: Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet. Locate control system networks and remote devices behind firewalls and isolating them from business networks. When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize 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 cisa.gov/ics. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies. CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets. Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B–Targeted Cyber Intrusion Detection and Mitigation Strategies. Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents. No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time.
5. UPDATE HISTORY August 21, 2025: Initial Publication