Siemens SINEC NMS Authentication Bypass Vulnerability, CVSS 7.3

ICS Advisory

Siemens SINEC NMS

Release Date

April 21, 2026

Alert Code ICSA-26-111-03 Related topics: Industrial Control System Vulnerabilities, Industrial Control Systems View CSAF

Summary

Siemens SINEC NMS when used with User Management Component (UMC) contains an authentication bypass vulnerability due to insufficient validation of user identity. This could allow an unauthenticated remote attacker to bypass authentication and gain unauthorized access to the application. Siemens has released a new version for SINEC NMS and recommends to update to the latest version.

The following versions of Siemens SINEC NMS are affected:

• SINEC NMS

CVSS	Vendor	Equipment	Vulnerabilities
v3 7.3	Siemens	Siemens SINEC NMS	Improper Verification of Cryptographic Signature

Background

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

Vulnerabilities

The affected application contains an authentication weakness due to insufficient validation of user identity in the UMC component. This could allow an unauthenticated remote attacker to bypass authentication and gain unauthorized access to the application. (ZDI-CAN-27564)

View CVE Details

Affected Products

Siemens SINEC NMS

Vendor:
Siemens Product Version:
SINEC NMS Product Status:
known_affected

Remediations

Vendor fix
Update to V4.0 SP3 or later version
https://support.industry.siemens.com/cs/ww/en/view/110000760/

Relevant CWE: CWE-347 Improper Verification of Cryptographic Signature

Metrics

CVSS Version	Base Score	Base Severity	Vector String
3.1	7.3	HIGH	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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-801704 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: 2026-04-14

Date	Revision	Summary
2026-04-14	1	Publication Date
2026-04-21	2	Initial CISA Republication of Siemens ProductCERT SSA-801704 advisory

Legal Notice and Terms of Use

This product is provided subject to this Notification and this Privacy & Use policy.

Vendor

• Siemens

Tags

Sector: Critical Manufacturing Sector Topics: Industrial Control System Vulnerabilities, Industrial Control Systems

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