CVE-2023-29131
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 < V2.5). Affected device consists of an incorrect default value in the SSH configuration. This could allow an attacker to bypass network isolation.
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 device ships with an insecure default SSH configuration value that weakens security controls, potentially allowing attackers to bypass network isolation protections and gain unauthorized access to the device or pivot to other systems.
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< 2.5CVSS 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
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 checksWork through these to decide whether this CVE applies to you.
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Confirm device model is SIMATIC CN 4100Access the device web interface or use Nmap/network scan to identify the device hostname, model number, or login banner. Look for 'SIMATIC CN 4100' or 'CN 4100' in the device identification.Affected if The device is a Siemens SIMATIC CN 4100 unit
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Check installed firmware versionLog into the device web interface or CLI and navigate to the firmware/software version information page. Alternatively, check via SNMP or the device's system information endpoint.Affected if Firmware version is below V2.5 (for example, V2.4, V2.3, V2.0, etc.)
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Verify SSH service is enabledCheck if SSH (port 22) is listening on the device using a network port scan (nmap -p 22 <device_ip>) or by reviewing the device services list in the web interface under 'Services' or 'Protocols'.Affected if SSH service is active and port 22 is open/accessible on the device
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Inspect SSH configuration for weak default settingsConnect to the device via SSH or console and review the SSH daemon configuration file (usually /etc/ssh/sshd_config or via web interface SSH settings). Look for security-weakening parameters such as weak authentication methods, disabled encryption, or permissive access controls set to default values.Affected if The SSH configuration contains insecure default values that weaken authentication or access controls
The environment is affected if the device is a SIMATIC CN 4100 running firmware version below V2.5 with SSH enabled and configured using the insecure default settings.
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 · scoped2.5
Upgrade SIMATIC CN 4100 to firmware version V2.5 or later. Additionally, implement compensating network controls such as firewall rules and VLAN segmentation to restrict SSH access to authorized management networks until the upgrade can be performed.
V2.5
- Check current firmware version on the SIMATIC CN 4100 device
- Download firmware version V2.5 or later from the official Siemens support portal (support.automation.siemens.com)
- Review the firmware upgrade instructions in the Siemens product documentation or release notes
- Perform the firmware upgrade following Siemens recommended procedures
- After upgrade, verify the SSH configuration has been corrected and the device is running V2.5 or later
- Confirm network isolation controls are functioning as expected
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-29131 — 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-2023-29131 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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