CVE-2023-4809
HIGHDescription
In pf packet processing with a 'scrub fragment reassemble' rule, a packet containing multiple IPv6 fragment headers would be reassembled, and then immediately processed. That is, a packet with multiple fragment extension headers would not be recognized as the correct ultimate payload. Instead a packet with multiple IPv6 fragment headers would unexpectedly be interpreted as a fragmented packet, rather than as whatever the real payload is. As a result, IPv6 fragments may bypass pf firewall rules written on the assumption all fragments have been reassembled and, as a result, be forwarded or processed by the host.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Exploit Intelligence
Moderate risk: more likely to be exploited than 49% of all known CVEs.
References
Related Vulnerabilities
Other CWE-167 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-25006 | Medium | 5.3 | 0.9% | - | Fix |
| CVE-2023-3580 | Medium | 4.3 | 0.6% | - | Fix |
| CVE-2023-0643 | Medium | 6.1 | 0.6% | - | Fix |
| CVE-2025-30656 | High | 7.5 | 0.4% | - | Fix |
Common questions
How do I fix CVE-2023-4809?
Upgrade freebsd to 13.2 or later.
Is CVE-2023-4809 being actively exploited?
Not that we know of. CVE-2023-4809 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.68% is the estimated probability that it will be exploited in the next 30 days. That is higher than 49% of all scored CVEs.
How severe is CVE-2023-4809?
CVE-2023-4809 has a CVSS v3 base score of 7.5, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2023-4809 affect?
Published advisories record a fix for freebsd (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-02-13.