# CVE-2023-4809

## Summary

- **CVE ID:** CVE-2023-4809
- **Severity:** UNKNOWN
- **CVSS Score:** 0.02
- **CWE:** CWE-167
- **Published:** Sep 6, 2023
- **Last Modified:** Mar 13, 2026

## Description

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.

## Affected Products

- FreeBSD — FreeBSD (13.2-RELEASE)
- FreeBSD — FreeBSD (12.4-RELEASE)

## References

- [CNA](https://security.FreeBSD.org/advisories/FreeBSD-SA-23:10.pf.asc)
- [CNA](http://www.openwall.com/lists/oss-security/2023/09/08/5)
- [CNA](http://www.openwall.com/lists/oss-security/2023/09/08/6)
- [CNA](http://www.openwall.com/lists/oss-security/2023/09/08/7)
- [CNA](https://security.netapp.com/advisory/ntap-20231221-0009/)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.47%
- **EPSS Percentile:** 64.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-12._