PatchSiren

PatchSiren cyber security CVE debrief

CVE-2025-40938 Siemens CVE debrief

CVE-2025-40938 affects Siemens SIMATIC CN 4100. According to the advisory, sensitive information is stored in firmware, which could let an attacker access and misuse it and potentially affect confidentiality, integrity, and availability. Siemens and CISA rate the issue as High severity, and Siemens provides a fixed version.

Vendor
Siemens
Product
SIMATIC CN 4100
CVSS
HIGH 8.1
CISA KEV
Not listed in stored evidence
Original CVE published
2025-12-09
Original CVE updated
2025-12-09
Advisory published
2025-12-09
Advisory updated
2025-12-09

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.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-40938 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-40938

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2025-40938 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-40938

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2026/icsa-26-015-12.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-416652.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-416652.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2025/icsa-26-015-12.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-26-015-12

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-alerts/ics-alert-10-301-01

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/resources-tools/resources/ics-recommended-practices

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/topics/industrial-control-systems

    Reference

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.