CVE-2023-6534

Name: CVE-2023-6534
Creator: NVD / NIST
Published: 2023-12-13T09:15:34.68+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.74%

Last modified Jun 17, 2026

CVE-2023-6534 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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.. EPSS estimates a 0.74% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.74%

50.0th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Freebsd	Freebsd	12.4
Freebsd	Freebsd	13.2
Freebsd	Freebsd	14.0

References

Timeline

Published: Dec 13, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-6534?

How severe is CVE-2023-6534?

CVE-2023-6534 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.74% probability of exploitation in the next 30 days.

How do I fix CVE-2023-6534?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2023-6534?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST