CVE-2025-40593
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 · uneditedA vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0). The affected application allows to control the device by storing arbitrary files in the SFTP folder of the device. This could allow an attacker to cause a denial of service condition.
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 confidenceThe SIMATIC CN 4100 application allows arbitrary file storage in its SFTP folder without proper validation. An attacker with SFTP access can upload files to fill storage or place malicious files, causing denial of service. The vulnerability exists in all versions prior to V4.0.
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< 4.0CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify the installed firmware versionLog into the SIMATIC CN 4100 web interface or use Siemens PRONETA/SIMATIC IT Tool to retrieve the current firmware version from the device diagnostics or system information page.Affected if The firmware version displayed is earlier than V4.0 (for example, V3.x or any version number below 4.0).
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Verify SFTP service statusAccess the device configuration panel and navigate to the Services or Communication settings to confirm whether the SFTP server is enabled on the device.Affected if The SFTP service is listed as enabled or active on the device.
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Inspect SFTP access controlsReview the SFTP user accounts and access permissions in the device security or user management settings. Check if anonymous or unauthenticated SFTP access is permitted.Affected if SFTP access is granted to users without proper authentication, or guest/anonymous accounts have write permissions to the SFTP folder.
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Check network exposure of SFTP portUse a network scanner or check the device firewall rules to determine if TCP port 22 (SFTP) is exposed to untrusted network segments or the internet.Affected if Port 22/SFTP is accessible from external or untrusted network zones.
A user is affected if the device runs firmware prior to V4.0 AND has SFTP enabled with accessible network exposure.
Generated from the published advisory. Verify against your own configuration.
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 · scoped4.0
Update SIMATIC CN 4100 to version V4.0 or later to obtain the patched firmware. If immediate patching is not possible, restrict SFTP access through network segmentation and enforce authentication for SFTP connections.
V4.0 or later
- Check current firmware version of the SIMATIC CN 4100 device
- Obtain firmware version V4.0 or later from Siemens official download portal (cert-portal.siemens.com or siemens.com)
- Review Siemens firmware update documentation for SIMATIC CN 4100
- Upload and install the V4.0 firmware following Siemens standard firmware upgrade procedure
- After reboot, verify the device is running firmware version V4.0 or later
- Confirm the SFTP service is functioning normally and the vulnerability is remediated
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-40593 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-40593 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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