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

2023-09-0619:26:45

CWE-167

freebsd

www.cve.org

cve-2023-4809

pf packet processing

ipv6 fragment headers

firewall rules

payload interpretation

security vulnerability

0.001 Low

EPSS

Percentile

21.4%

JSON

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.

CNA Affected

[
  {
    "defaultStatus": "unknown",
    "modules": [
      "pf"
    ],
    "product": "FreeBSD",
    "vendor": "FreeBSD",
    "versions": [
      {
        "lessThan": "p3",
        "status": "affected",
        "version": "13.2-RELEASE",
        "versionType": "release"
      },
      {
        "lessThan": "p5",
        "status": "affected",
        "version": "12.4-RELEASE",
        "versionType": "release"
      }
    ]
  }
]