OpenBSD kernel version <= 6.5 can be forced to create long chains of TCP SACK holes that causes very expensive calls to tcp_sack_option() for every incoming SACK packet which can lead to a denial of service. Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-8460 Reference (s):
- https://security.netapp.com/advisory/ntap-20190905-0001/
- https://ftp.openbsd.org/pub/OpenBSD/patches/6.5/common/006_tcpsack.patch.sig
- https://github.com/openbsd/src/commit/ed8fdce754a5d8d14c09e989d8877707bd43906f
- https://research.checkpoint.com/tcp-sack-security-issue-in-openbsd-cve-2019-8460/
- https://us-cert.cisa.gov/ics/advisories/icsa-19-253-03