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Summary

Siemens ET 200SP contains a denial-of-service vulnerability that could be triggered by sending a valid S7 protocol Disconnect Request (COTP DR TPDU), causing the device to become unresponsive and require a power cycle to recover. Siemens has released new versions for several affected products and recommends to update to the latest versions. Siemens is preparing further fix versions and recommends specific countermeasures for products where fixes are not, or not yet available.

The following versions of Siemens SIMATIC and SIPLUS products are affected:

• SIMATIC ET 200AL IM 157-1 PN (6ES7157-1AB00-0AB0) (CVE-2025-40944)
• SIMATIC ET 200MP IM 155-5 PN HF (6ES7155-5AA00-0AC0) (CVE-2025-40944)
• SIMATIC ET 200SP IM 155-6 MF HF (6ES7155-6MU00-0CN0) (CVE-2025-40944)
• SIMATIC ET 200SP IM 155-6 PN HA (incl. SIPLUS variants) (CVE-2025-40944)
• SIMATIC ET 200SP IM 155-6 PN R1 (6ES7155-6AU00-0HM0) (CVE-2025-40944)
• SIMATIC ET 200SP IM 155-6 PN/2 HF (6ES7155-6AU01-0CN0) (CVE-2025-40944)
• SIMATIC ET 200SP IM 155-6 PN/3 HF (6ES7155-6AU30-0CN0) (CVE-2025-40944)
• SIMATIC PN/MF Coupler (6ES7158-3MU10-0XA0) (CVE-2025-40944)
• SIMATIC PN/PN Coupler (6ES7158-3AD10-0XA0) (CVE-2025-40944)
• SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-2AC0) (CVE-2025-40944)
• SIPLUS ET 200MP IM 155-5 PN HF (6AG1155-5AA00-7AC0) (CVE-2025-40944)
• SIPLUS ET 200MP IM 155-5 PN HF T1 RAIL (6AG2155-5AA00-1AC0) (CVE-2025-40944)
• SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-2CN0) (CVE-2025-40944)
• SIPLUS ET 200SP IM 155-6 PN HF (6AG1155-6AU01-7CN0) (CVE-2025-40944)
• SIPLUS ET 200SP IM 155-6 PN HF T1 RAIL (6AG2155-6AU01-1CN0) (CVE-2025-40944)
• SIPLUS ET 200SP IM 155-6 PN HF TX RAIL (6AG2155-6AU01-4CN0) (CVE-2025-40944)
• SIPLUS NET PN/PN Coupler (6AG2158-3AD10-4XA0) (CVE-2025-40944)

Background

• Critical Infrastructure Sectors: Critical Manufacturing
• Countries/Areas Deployed: Worldwide
• Company Headquarters Location: Germany

Vulnerabilities

Acknowledgments

• Siemens ProductCERT reported this vulnerability to CISA.

General Recommendations

As a general security measure, Siemens strongly recommends to protect network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends to configure the environment according to Siemens’ operational guidelines for Industrial Security (Download: https://www.siemens.com/cert/operational-guidelines-industrial-security), and to follow the recommendations in the product manuals. Additional information on Industrial Security by Siemens can be found at: https://www.siemens.com/industrialsecurity

Additional Resources

For further inquiries on security vulnerabilities in Siemens products and solutions, please contact the Siemens ProductCERT: https://www.siemens.com/cert/advisories

Terms of Use

The use of Siemens Security Advisories is subject to the terms and conditions listed on: https://www.siemens.com/productcert/terms-of-use.

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 Siemens ProductCERT SSA-674753 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 Siemens ProductCERT directly for any questions regarding this advisory.

Revision History

• Initial Release Date: 2026-01-13

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