high
7.5
CWE
167
Advisory Published
Updated

CVE-2023-4809: pf incorrectly handles multiple IPv6 fragment headers

First published: Wed Sep 06 2023(Updated: )

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.

Credit: secteam@freebsd.org

Affected SoftwareAffected VersionHow to fix
FreeBSD Kernel<12.4
FreeBSD Kernel>=13.0<13.2
FreeBSD Kernel=12.4
FreeBSD Kernel=12.4-p1
FreeBSD Kernel=12.4-p2
FreeBSD Kernel=12.4-p3
FreeBSD Kernel=12.4-p4
FreeBSD Kernel=12.4-rc2-p1
FreeBSD Kernel=12.4-rc2-p2
FreeBSD Kernel=13.2
FreeBSD Kernel=13.2-p1
FreeBSD Kernel=13.2-p2

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Reference Links

Frequently Asked Questions

  • What is the severity of CVE-2023-4809?

    CVE-2023-4809 has been classified with a severity level that indicates it poses a significant security risk to affected FreeBSD versions.

  • How do I fix CVE-2023-4809?

    To address CVE-2023-4809, users should update to the latest patched version of FreeBSD that resolves the vulnerability.

  • Which FreeBSD versions are affected by CVE-2023-4809?

    CVE-2023-4809 affects FreeBSD versions 12.4 and versions between 13.0 and 13.2.

  • What is the nature of the vulnerability in CVE-2023-4809?

    CVE-2023-4809 involves an issue in pf packet processing where multiple IPv6 fragment headers can be improperly reassembled.

  • Is there a workaround for CVE-2023-4809 until I can update?

    While no specific workarounds are recommended, avoiding the use of affected features until an update can be applied may help mitigate risks.

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