{"id":"CVE-2023-4809","aliases":["EUVD-2023-54653","GHSA-g6hh-x63c-83gf"],"status":"published","title":"pf incorrectly handles multiple IPv6 fragment headers","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.\n\n\n\n\nAs 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.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-09","score":0.00802,"percentile":0.56921,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-167"],"published":"2023-09-06T19:26:45Z","modified":"2026-06-17T06:38:37Z","products":[{"vendor":"freebsd","product":"freebsd"}],"references":[{"url":"https://security.FreeBSD.org/advisories/FreeBSD-SA-23:10.pf.asc","tags":["vendor-advisory","x_transferred","Vendor Advisory"]},{"url":"http://www.openwall.com/lists/oss-security/2023/09/08/5","tags":["x_transferred","Mailing List","Third Party Advisory"]},{"url":"http://www.openwall.com/lists/oss-security/2023/09/08/6","tags":["x_transferred","Mailing List","Third Party Advisory"]},{"url":"http://www.openwall.com/lists/oss-security/2023/09/08/7","tags":["x_transferred","Mailing List","Third Party Advisory"]},{"url":"https://security.netapp.com/advisory/ntap-20231221-0009/","tags":["x_transferred"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-4809"},{"url":"https://security.netapp.com/advisory/ntap-20231221-0009"},{"url":"https://github.com/advisories/GHSA-g6hh-x63c-83gf"}],"sources":{"cve":[{"id":"CVE-2023-4809","title":"pf incorrectly handles multiple IPv6 fragment headers","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.\n\n\n\n\nAs 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.","status":"published","published":"2023-09-06T19:26:45.833Z","modified":"2025-02-13T17:18:10.982Z","cwes":["CWE-167"],"updated_at":"2026-11-02T14:35:30.851125Z"}],"euvd":[{"id":"EUVD-2023-54653","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.\n\n\n\n\nAs 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.","status":"published","published":"2023-09-06T19:26:45Z","modified":"2025-02-13T17:18:10Z","updated_at":"2026-11-03T00:03:48.562419Z"}],"ghsa":[{"id":"GHSA-g6hh-x63c-83gf","title":"In pf packet processing with a 'scrub fragment reassemble' rule, a packet containing multiple...","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.\n\n\n\n\nAs 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.","status":"published","published":"2023-09-06T21:32:50Z","modified":"2025-02-13T18:32:52Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"cwes":["CWE-167"],"updated_at":"2026-11-02T14:59:55.900946Z"}],"nvd":[{"id":"CVE-2023-4809","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.\n\n\n\n\nAs 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.","status":"published","published":"2023-09-06T20:15:08.08Z","modified":"2026-06-17T06:38:37.91Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"primary"}],"cwes":["CWE-167"],"updated_at":"2026-11-02T14:08:28.268644Z"}]}}