In NetBSD through 9.2, the IPv4 ID generation algorithm does not use appropriate cryptographic measures.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-32253
https://arxiv.org/pdf/2112.09604.pdf
http://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2021-001.txt.asc