CVE-2018-4851
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 SICLOCK TC100 (All versions) and SICLOCK TC400 (All versions). An attacker with network access to the device could cause a Denial-of-Service condition by sending certain packets to the device, causing potential reboots of the device. The core functionality of the device could be impacted. The time serving functionality recovers when time synchronization with GPS devices or other NTP servers are completed.
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 · high confidenceA denial-of-service vulnerability exists in SICLOCK TC100 and TC400 time clock devices where an attacker with network access can send specially crafted packets that cause the device to reboot, impacting core time-serving functionality until time synchronization with GPS or NTP servers completes.
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 dataall versionsall versionsCVSS 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
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 SICLOCK devices on your networkPerform network discovery scanning (e.g., nmap, network inventory tools) to detect Siemens SICLOCK TC100 or TC400 time clock devices. Look for device signatures, MAC OUI (Siemens), or management ports commonly used by these devices.Affected if SICLOCK TC100 or TC400 time clock devices are found on the network
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Verify device firmware version via management interfaceIf you have administrative access, log into the device web interface or management console and check the firmware version under system information or device status. Compare against 'all versions' known to be affected.Affected if The device is a SICLOCK TC100 or TC400 running any firmware version
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Assess network exposure of SICLOCK devicesReview firewall rules, network segmentation, and ACLs to determine if the SICLOCK devices management interfaces are reachable from untrusted networks or the internet. Check if ports used by these devices (typically HTTP/HTTPS for management) are exposed to external networks.Affected if The SICLOCK device management interface is accessible from untrusted or external networks without proper filtering
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Check for anomalous device behaviorReview system logs, network logs, or SIEM alerts for evidence of unexpected device reboots, loss of NTP/GPS sync, or unusual traffic patterns targeting the SICLOCK device IP addresses.Affected if Device is experiencing unexplained reboots or time synchronization failures coinciding with suspicious network traffic
You are affected if you have any SICLOCK TC100 or TC400 time clock devices on your network that are accessible from untrusted network segments, as all firmware versions contain the vulnerability.
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.
From vendor dataImplement network segmentation and firewall rules to restrict unauthorized network access to the SICLOCK devices; monitor for anomalous traffic patterns indicative of DoS attempts.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-4851 — 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-2018-4851 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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