# CVE-2023-6534: TCP spoofing vulnerability in pf(4)

> Attackers can spoof TCP packets to bypass pf firewall validation, causing denial of service for hosts behind the firewall.

- **Severity:** High 7.5 (`CVSS:3.1/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:** 13 Dec 2023
- **Updated:** 13 Feb 2025
- **Also known as:** GHSA-v254-5m89-3qf2

## What is CVE-2023-6534?

CVE-2023-6534 is a high-severity denial of service vulnerability in Freebsd Freebsd, published on 13 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In versions of FreeBSD 14.0-RELEASE before 14-RELEASE-p2, FreeBSD 13.2-RELEASE before 13.2-RELEASE-p7 and FreeBSD 12.4-RELEASE before 12.4-RELEASE-p9, the pf(4) packet filter incorrectly validates TCP sequence numbers.  This could allow a malicious actor to execute a denial-of-service attack against hosts behind the firewall.

## Which versions are affected by CVE-2023-6534?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2023-6534?

No fix has been published for CVE-2023-6534 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-6534 being exploited?

There is no known exploitation of CVE-2023-6534 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-2023-6534 and fix it if it is affected.

What it is: CVE-2023-6534 is a high-severity denial of service vulnerability in Freebsd Freebsd, published on 13 Dec 2023. 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-2023-6534 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-2023-6534/ (Markdown: https://insights.sbomify.com/CVE-2023-6534/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-6534
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-6534
- OSV: https://osv.dev/vulnerability/CVE-2023-6534

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-6534/
Summaries are generated and may contain mistakes; the official description above is the record.