# CVE-2018-6918: Denial of service in FreeBSD

> A remote attacker can crash the system by sending a crafted packet with a zero-length IPsec option header, causing an infinite loop.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 4 Apr 2018
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-v4xf-p7r4-pfpq

## What is CVE-2018-6918?

CVE-2018-6918 is a high-severity denial of service vulnerability in Freebsd Freebsd, published on 4 Apr 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In FreeBSD before 11.1-STABLE, 11.1-RELEASE-p9, 10.4-STABLE, 10.4-RELEASE-p8 and 10.3-RELEASE-p28, the length field of the ipsec option header does not count the size of the option header itself, causing an infinite loop when the length is zero. This issue can allow a remote attacker who is able to send an arbitrary packet to cause the machine to crash.

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2018-6918?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2018-6918?

No fix has been published for CVE-2018-6918 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-6918 being exploited?

There is no known exploitation of CVE-2018-6918 in the wild and no public exploit code.

## Other vulnerabilities in Freebsd Freebsd

- [CVE-2018-17160](https://insights.sbomify.com/CVE-2018-17160/): Memory corruption in FreeBSD (critical 10.0)
- [CVE-2014-3954](https://insights.sbomify.com/CVE-2014-3954/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-4304](https://insights.sbomify.com/CVE-2006-4304/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-0226](https://insights.sbomify.com/CVE-2006-0226/): Integer overflow in n/a (critical 10.0)
- [CVE-2004-0002](https://insights.sbomify.com/CVE-2004-0002/): Denial of service in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-6918 and fix it if it is affected.

What it is: CVE-2018-6918 is a high-severity denial of service vulnerability in Freebsd Freebsd, published on 4 Apr 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-2018-6918 in the wild and no public exploit code.

Affected product: Freebsd Freebsd. 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-2018-6918/ (Markdown: https://insights.sbomify.com/CVE-2018-6918/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-6918
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-6918
- OSV: https://osv.dev/vulnerability/CVE-2018-6918

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-6918/
Summaries are generated and may contain mistakes; the official description above is the record.