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PatchSiren cyber security CVE debrief

CVE-2025-40937 Siemens CVE debrief

CVE-2025-40937 affects Siemens SIMATIC CN 4100 and was publicly published on 2025-12-09. According to the CISA CSAF advisory, the application does not properly validate input parameters in its REST API, which can lead to improper handling of unexpected arguments. Siemens and CISA describe the impact as a condition that could allow an authenticated attacker to execute arbitrary code with limited privileges. Siemens provides a fix in version V4.0.1 or later.

Vendor
Siemens
Product
SIMATIC CN 4100
CVSS
HIGH 8.3
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

Organizations running Siemens SIMATIC CN 4100, especially industrial control system operators, plant administrators, and security teams responsible for authenticated service access and vendor patch management.

Technical summary

The advisory describes a REST API input validation weakness in SIMATIC CN 4100. The CVSS vector provided is CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L, indicating network-reachable impact, low attack complexity, and required low privileges. The stated outcome is possible arbitrary code execution with limited privileges through improper handling of unexpected arguments.

Defensive priority

High. The CVSS score is 8.3 and the affected product is an ICS-related Siemens system with a vendor fix available. Prioritize patching and exposure reduction for any deployments where authenticated REST API access is reachable.

Recommended defensive actions

  • Update Siemens SIMATIC CN 4100 to V4.0.1 or later as recommended by the vendor.
  • Review which administrators or services can authenticate to the product's REST API and restrict access to the minimum necessary.
  • Apply industrial-control defense-in-depth practices and limit network reachability to management interfaces where possible.
  • Monitor Siemens and CISA advisory channels for any follow-on guidance related to ICSA-26-015-12 / SSA-416652.
  • Validate that asset inventories and patch records reflect the affected product and the remediation version.

Evidence notes

Source details come from the supplied CISA CSAF record for ICSA-26-015-12 and the referenced Siemens advisory SSA-416652. The advisory states the REST API parameter-validation issue and the potential for authenticated arbitrary code execution with limited privileges. The supplied CVSS vector is CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L, and the remediation listed is V4.0.1 or later. KEV status in the supplied enrichment is false.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-40937 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-40937

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

  • CVE-2025-40937 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-40937

    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.