Linux kernel versions 4.9+ can be forced to make very expensive calls to tcp_collapse_ofo_queue() and tcp_prune_ofo_queue() for every incoming packet which can lead to a denial of service.
https://access.redhat.com/errata/RHSA-2018:2384
https://access.redhat.com/errata/RHSA-2018:2395
https://access.redhat.com/errata/RHSA-2018:2402
https://access.redhat.com/errata/RHSA-2018:2403
https://access.redhat.com/errata/RHSA-2018:2645
https://access.redhat.com/errata/RHSA-2018:2776
https://access.redhat.com/errata/RHSA-2018:2785
https://access.redhat.com/errata/RHSA-2018:2789
https://access.redhat.com/errata/RHSA-2018:2790
https://access.redhat.com/errata/RHSA-2018:2791
https://access.redhat.com/errata/RHSA-2018:2924
https://access.redhat.com/errata/RHSA-2018:2933
https://access.redhat.com/errata/RHSA-2018:2948
https://cert-portal.siemens.com/productcert/pdf/ssa-377115.pdf
https://lists.debian.org/debian-lts-announce/2018/08/msg00014.html
https://security.netapp.com/advisory/ntap-20180815-0003/
https://support.f5.com/csp/article/K95343321
https://support.f5.com/csp/article/K95343321?utm_source=f5support&%3Butm_medium=RSS
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180824-linux-tcp
https://usn.ubuntu.com/3732-1/
https://usn.ubuntu.com/3732-2/
https://usn.ubuntu.com/3741-1/
https://usn.ubuntu.com/3741-2/
https://usn.ubuntu.com/3742-1/
https://usn.ubuntu.com/3742-2/
https://usn.ubuntu.com/3763-1/
https://www.debian.org/security/2018/dsa-4266
https://www.kb.cert.org/vuls/id/962459
https://www.oracle.com/security-alerts/cpujul2020.html
https://www.oracle.com/technetwork/security-advisory/cpujan2019-5072801.html
http://www.huawei.com/en/psirt/security-advisories/huawei-sa-20181031-02-linux-en
http://www.openwall.com/lists/oss-security/2019/06/28/2
http://www.openwall.com/lists/oss-security/2019/07/06/3
http://www.openwall.com/lists/oss-security/2019/07/06/4