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Simatic Cn 4100 FirmwareOperating system · Siemens

CVE-2025-40937

HIGH · 8.8 CVSS v3.1 Published 2025-12-09
Fix available
A fix is available. Upgrade to 4.0.1 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0.1). The affected application do not properly validate input parameters in its REST API, resulting in improper handling of unexpected arguments. This could allow an authenticated attacker to execute arbitrary code with limited privileges.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

The SIMATIC CN 4100 REST API fails to properly validate input parameters, allowing authenticated attackers to inject unexpected arguments that lead to arbitrary code execution with limited privileges. This is an authenticated remote code execution vulnerability in the web API layer.

MitigationUpgrade SIMATIC CN 4100 to version V4.0.1 or later to obtain the vendor patch. Additionally, restrict REST API access to only necessary authenticated users and monitor for anomalous API calls.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Simatic Cn 4100 FirmwareOperating system
Affected:< 4.0.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the SIMATIC CN 4100 firmware version
    Log into the device web interface, admin console, or access via SSH to retrieve the current firmware version information. Look for a version or build number in the system info or about section.
    Affected if The installed firmware version is below 4.0.1 (for example, 4.0.0, 3.x, or any version number less than 4.0.1).
  2. Confirm REST API is enabled and accessible
    Check the device configuration to verify whether the REST API service is enabled. This may be visible in the web interface under services, API settings, or network configuration.
    Affected if The REST API is enabled and exposed on the network.
  3. Verify REST API authentication configuration
    Review the REST API user accounts and authentication settings. Check if default or weak credentials are in use, and confirm which user privilege levels have API access.
    Affected if The REST API permits authenticated access with user accounts that have privileges sufficient to make API calls.
  4. Inspect API access logs for anomalous requests
    Review the device logs, API access logs, or audit logs for unusual or unexpected API calls, especially those containing unusual parameter patterns or command-like strings.
    Affected if Logs show API calls with injected arguments or unexpected parameter values that could indicate exploitation attempts.

The environment is affected if the SIMATIC CN 4100 firmware version is below 4.0.1 and the REST API is enabled with accessible authenticated user accounts.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.0.1 or later
Fixed in 4.0.1
Interim mitigation

Upgrade SIMATIC CN 4100 to version V4.0.1 or later to obtain the vendor patch. Additionally, restrict REST API access to only necessary authenticated users and monitor for anomalous API calls.

Recommended fix High confidence

V4.0.1

  1. 1. Identify the current firmware version of the Simatic CN 4100 device by accessing the device management interface or checking system information.
  2. 2. Navigate to the Siemens support portal (cert-portal.siemens.com or siemens.com) and locate the SIMATIC CN 4100 firmware V4.0.1 or later.
  3. 3. Download the firmware update package for V4.0.1, ensuring you review any associated release notes for update instructions.
  4. 4. Follow the standard Siemens firmware update procedure for the Simatic CN 4100 device: typically involves accessing the device's web-based management interface or using the appropriate update tool, uploading the firmware file, and initiating the update process.
  5. 5. After the update completes, verify the device is running firmware V4.0.1 or later and confirm normal operation.
  6. 6. Test the REST API functionality to ensure the input validation fixes are working correctly.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Simatic Cn 4100 Firmware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
20.0 hours of engineering $3,440
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-40937 in production — separate from our analysis above.

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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