# CVE-2018-4851: Denial of service in SICLOCK TC100, SICLOCK TC400

> An attacker can cause a denial-of-service condition on SICLOCK time servers by sending specific network packets, leading to device reboots.

- **Severity:** High 8.2 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 3 Jul 2018
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-x4qq-cpcc-jfwx

## What is CVE-2018-4851?

CVE-2018-4851 is a high-severity denial of service vulnerability in Siemens AG SICLOCK TC100, SICLOCK TC400, published on 3 Jul 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A 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.

Weakness: CWE-20 (Improper Input Validation), CWE-399

## Which versions are affected by CVE-2018-4851?

It affects 2 products.


Products: Siemens Siclock Tc100 Firmware, Siemens Siclock Tc400 Firmware.

## How do I fix CVE-2018-4851?

No fix has been published for CVE-2018-4851 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-4851 being exploited?

There is no known exploitation of CVE-2018-4851 in the wild and no public exploit code.

## Other vulnerabilities in Siemens AG SICLOCK TC100, SICLOCK TC400

- [CVE-2018-4852](https://insights.sbomify.com/CVE-2018-4852/): Auth bypass in SICLOCK TC100, SICLOCK TC400 (critical 9.8)
- [CVE-2018-4853](https://insights.sbomify.com/CVE-2018-4853/): Missing authorization in SICLOCK TC100, SICLOCK TC400 (critical 9.8)
- [CVE-2018-4854](https://insights.sbomify.com/CVE-2018-4854/): Missing authorization in SICLOCK TC100, SICLOCK TC400 (high 8.8)
- [CVE-2018-4855](https://insights.sbomify.com/CVE-2018-4855/): Information disclosure in SICLOCK TC100, SICLOCK TC400 (medium 6.5)
- [CVE-2018-4856](https://insights.sbomify.com/CVE-2018-4856/): Auth bypass in SICLOCK TC100, SICLOCK TC400 (medium 4.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-4851 and fix it if it is affected.

What it is: CVE-2018-4851 is a high-severity denial of service vulnerability in Siemens AG SICLOCK TC100, SICLOCK TC400, published on 3 Jul 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2018-4851 in the wild and no public exploit code.

Affected product: Siemens AG SICLOCK TC100, SICLOCK TC400. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2018-4851/ (Markdown: https://insights.sbomify.com/CVE-2018-4851/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-4851
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-4851
- OSV: https://osv.dev/vulnerability/CVE-2018-4851

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-4851/
Summaries are generated and may contain mistakes; the official description above is the record.