Summary
Successful exploitation of this vulnerability could allow a remote attacker to cause a denial-of-service (DoS) condition in the affected product by rapidly establishing a large number of TCP connections to it, resulting in an inconsistency in the product’s internal connection management process and triggering improper memory access.
The following versions of Mitsubishi Electric MELSEC iQ-F Series are affected:
- MELSEC iQ-F Series FX5-EIP EtherNet/IP Module FX5-EIP <=1.000 (CVE-2026-8805)
| CVSS | Vendor | Equipment | Vulnerabilities |
|---|---|---|---|
| v3 7.5 | Mitsubishi Electric | Mitsubishi Electric MELSEC iQ-F Series | Integer Overflow or Wraparound |
Background
- Critical Infrastructure Sectors: Critical Manufacturing
- Countries/Areas Deployed: Worldwide
- Company Headquarters Location: Japan
Vulnerabilities
CVE-2026-8805
An integer overflow or wraparound vulnerability exists in the EtherNet/IP function of MELSEC iQ-F Series EtherNet/IP module. This vulnerability could allow a remote attacker to cause a denial-of-service condition in the affected product by rapidly establishing a large number of TCP connections to it, resulting in an inconsistency in the product’s internal connection management process and triggering improper memory access.
Affected Products
Mitsubishi Electric MELSEC iQ-F Series
Mitsubishi Electric
Mitsubishi Electric MELSEC iQ-F Series FX5-EIP EtherNet/IP Module FX5-EIP: <=1.000
known_affected
Remediations
Vendor fix
Mitsubishi Electric is releasing fixed version 1.001 or later for MELSEC iQ-F Series FX5-EIP EtherNet/IP Module FX5-EIP. Download the update file for the fixed version from the link “https://www.mitsubishielectric.com/fa/download/index.html” and install it. For more information on the fixed version, refer to the Mitsubishi Electric security advisory at “https://www.mitsubishielectric.com/psirt/vulnerability/pdf/2026-002_en.pdf”.
https://www.mitsubishielectric.com/fa/download/index.html
Mitigation
For users who cannot immediately update the product, Mitsubishi Electric recommends using a firewall, virtual private network (VPN), etc. to prevent unauthorized access when internet access is required, to minimize the risk of exploiting this vulnerability.
Mitigation
For users who cannot immediately update the product, Mitsubishi Electric recommends using the affected product within a LAN and blocking access from untrusted networks and hosts through firewalls, to minimize the risk of exploiting this vulnerability.
Mitigation
For users who cannot immediately update the product, Mitsubishi Electric recommends using the IP filter function of the affected product to block access from untrusted hosts and minimize the risk of exploiting this vulnerability. For details on the IP filter function, refer to “13.1 IP Filter Function” in the MELSEC iQ-F FX5 User’s Manual (Communication) which can be downloaded from the link “https://www.mitsubishielectric.com/fa/download/index.html.”
https://www.mitsubishielectric.com/fa/download/index.html
Mitigation
For users who cannot immediately update the product, Mitsubishi Electric recommends restricting physical access to the affected product, as well as to PCs and network devices to which it is connected, to minimize the risk of exploiting this vulnerability.
Mitigation
For users who cannot immediately update the product, Mitsubishi Electric recommends installing anti-virus software on PCs that can access the affected product, to minimize the risk of exploiting this vulnerability.
Relevant CWE: CWE-190 Integer Overflow or Wraparound
Metrics
| CVSS Version | Base Score | Base Severity | Vector String |
|---|---|---|---|
| 3.1 | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 4.0 | 8.7 | HIGH | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
Acknowledgments
- Mitsubishi Electric reported this vulnerability to CISA.
Legal Notice and Terms of Use
This product is provided subject to this Notification (https://www.cisa.gov/notification) and this Privacy & Use policy (https://www.cisa.gov/privacy-policy).
Recommended Practices
CISA recommends users take defensive measures to minimize the exploitation risk of these vulnerabilities. Minimize network exposure for all control system devices and/or systems, and ensure they are not accessible from the internet. Locate control system networks and remote devices behind firewalls and isolate 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 recent version available. Also recognize VPN is only as secure as its 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. 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 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.
Advisory Conversion Disclaimer
This ICSA is a verbatim republication of Mitsubishi Electric 2026-002 from a direct conversion of the vendor’s Common Security Advisory Framework (CSAF) advisory. This is republished to CISA’s website as a means of increasing visibility and is provided “as-is” for informational purposes only. CISA is not responsible for the editorial or technical accuracy of republished advisories and provides no warranties of any kind regarding any information contained within this advisory. Further, CISA does not endorse any commercial product or service. Please contact Mitsubishi Electric directly for any questions regarding this advisory.
Revision History
- Initial Release Date: 2026-06-18
| Date | Revision | Summary |
|---|---|---|
| 2026-06-18 | 1 | Initial Publication |
| 2026-06-18 | 2 | Initial CISA Republication of Mitsubishi Electric 2026-002 advisory |