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FreeBSD: VID-D35373AE-4D34-11EE-8E38-002590C1F29C (CVE-2023-4809): FreeBSD -- pf incorrectly handles multiple IPv6 fragment headers

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FreeBSD: VID-D35373AE-4D34-11EE-8E38-002590C1F29C (CVE-2023-4809): FreeBSD -- pf incorrectly handles multiple IPv6 fragment headers

Severity
4
CVSS
(AV:L/AC:M/Au:N/C:P/I:P/A:P)
Published
09/06/2023
Created
09/08/2023
Added
09/07/2023
Modified
09/15/2023

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.

Solution(s)

  • freebsd-upgrade-base-12_4-release-p5
  • freebsd-upgrade-base-13_2-release-p3

References

  • CVE-2023-4809

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