CVE-2025-40938 Siemens CVE debrief

Who should care

Operators and owners of Siemens SIMATIC CN 4100 devices, OT/ICS security teams, system integrators, and any environment where this product is deployed in production or connected to wider networks.

Technical summary

The advisory states that the affected device stores sensitive information in the firmware. If an attacker can access that data, it may be misused to impact confidentiality, integrity, and availability. The supplied CVSS vector is CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H, with a score of 8.1 (High). Siemens lists remediation as updating to V4.0.1 or later.

Defensive priority

High. This is a firmware data exposure issue on an OT device, and the provided advisory indicates potential impact across confidentiality, integrity, and availability. Prioritize patching and exposure reduction for any deployed SIMATIC CN 4100 instances.

Recommended defensive actions

• Update Siemens SIMATIC CN 4100 to V4.0.1 or later as directed by the vendor advisory.
• Inventory all affected SIMATIC CN 4100 devices and confirm current firmware versions before scheduling maintenance.
• Restrict network exposure to OT devices and limit access to trusted administrative paths only.
• Review Siemens and CISA industrial control system recommended practices for segmentation, hardening, and defense in depth.
• Verify backups and recovery procedures for impacted environments before making firmware changes.

Evidence notes

All conclusions are based on the supplied CISA CSAF advisory text and the referenced Siemens remediation notice. The source corpus identifies Siemens as the vendor, SIMATIC CN 4100 as the product, CVSS 8.1 High with vector AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H, and remediation by updating to V4.0.1 or later. No exploit details or confirmed real-world exploitation were provided in the source corpus.

Official resources