In NetBSD through 9.2, there is an information leak in the TCP ISN (ISS) generation algorithm.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-32254
https://arxiv.org/pdf/2112.09604.pdf
http://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2021-001.txt.asc