nginx before versions 1.15.6 and 1.14.1 has a vulnerability in the implementation of HTTP/2 that can allow for excessive CPU usage. This issue affects nginx compiled with the ngx_http_v2_module (not compiled by default) if the 'http2' option of the 'listen' directive is used in a configuration file.
http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00035.html
https://access.redhat.com/errata/RHSA-2018:3680
https://access.redhat.com/errata/RHSA-2018:3681
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-16844
http://seclists.org/fulldisclosure/2021/Sep/36
https://support.apple.com/kb/HT212818
https://usn.ubuntu.com/3812-1/