Mitsubishi Electric MELSEC-Q Series CPU Module

View CSAF

1. EXECUTIVE SUMMARY

• CVSS v3.1 6.8
• ATTENTION: Exploitable remotely
• Vendor: Mitsubishi Electric
• Equipment: MELSEC-Q Series CPU module
• Vulnerability: Improper Handling of Length Parameter Inconsistency

2. RISK EVALUATION

Successful exploitation of this vulnerability could allow an attacker to cause a denial of service (DoS).

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following versions of Mitsubishi Electric MELSEC-Q Series CPU modules are affected:

• MELSEC-Q Series Q03UDVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q04UDVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q06UDVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q13UDVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q26UDVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q04UDPVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q06UDPVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q13UDPVCPU: The first 5 digits of serial No. '24082' to '27081'
• MELSEC-Q Series Q26UDPVCPU: The first 5 digits of serial No. '24082' to '27081'

3.2 VULNERABILITY OVERVIEW

3.2.1 Improper Handling of Length Parameter Inconsistency CWE-130

A Denial-of-Service (DoS) vulnerability exists in the MELSEC-Q series CPU module when the user authentication function is enabled, due to improper handling of length parameter inconsistency.

CVE-2025-8531 has been assigned to this vulnerability. A CVSS v3.1 base score of 6.8 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:C/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 has released the fixed version as shown below, but updating the product to the fixed version is currently unavailable. Consider migrating to the successor model, MELSEC iQ-R Series.

• MELSEC-QSeries Q03UDVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q04UDVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q06UDVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q13UDVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q26UDVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q04UDPVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q06UDPVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q13UDPVCPU: The first 5 digits of serial No. '27082' or later.
• MELSEC-QSeries Q26UDPVCPU: The first 5 digits of serial No. '27082' or later.

Mitsubishi Electric recommends users employ the following mitigation measures to minimize the risk of vulnerability exploit.

• 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.
• Restrict physical access to the affected products, as well as to computers and network devices that can be connected to those products.

See Mitsubishi Electric's security bulletin for more information.

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. This vulnerability has a high attack complexity.

5. UPDATE HISTORY

• September 23, 2025: Initial Publication

• Mitsubishi Electric