The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the Protocols configuration includes h2 or h2c, does not restrict request-header length, which allows remote attackers to cause a denial of service (memory consumption) via crafted CONTINUATION frames in an HTTP/2 request.
https://www.tenable.com/security/tns-2017-04
https://support.apple.com/HT208221
https://security.netapp.com/advisory/ntap-20180423-0001/
https://security.gentoo.org/glsa/201701-36
https://h20566.www2.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03725en_us
https://github.com/apache/httpd/commit/29c63b786ae028d82405421585e91283c8fa0da3
https://access.redhat.com/errata/RHSA-2017:1414
https://access.redhat.com/errata/RHSA-2017:1413
https://access.redhat.com/errata/RHSA-2017:1161
http://www.securitytracker.com/id/1037388