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

High 7.5 Published 13 Dec 2023 Updated 13 Feb 2025

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

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

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 include 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.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2023-6534 being exploited?

There is no known exploitation of CVE-2023-6534 in the wild and no public exploit code.

All Freebsd Freebsd vulnerabilities

Sources

Also known as GHSA-v254-5m89-3qf2.