HAProxy packages shipped with Red Hat Enterprise Linux 6 and 7 do not contain support for HTTP/2; therefore, they are not affected by this flaw.
OpenShift Container Platform versions through 4.3 contain the vulnerable code; exploitation requires setting ROUTER_USE_HTTP2 in the OpenShift Ingress Operator, which is not currently possible. The impact of this vulnerability is therefore reduced in OCP 4.x, prior to version 4.4, to low.
OpenShift Container Platform 3.11 added a configuration option to ose-haproxy-router that made enabling HTTP/2 support easy. However, it is not enabled by default on that version.
In hpack_dht_insert in hpack-tbl.c in the HPACK decoder in HAProxy 1.8 through 2.x before 2.1.4, a remote attacker can write arbitrary bytes around a certain location on the heap via a crafted HTTP/2 request, possibly causing remote code execution.
A flaw was found in the way HAProxy processed certain HTTP/2 request packets. This flaw allows an attacker to send crafted HTTP/2 request packets, which cause memory corruption, leading to a crash or potential remote arbitrary code execution with the permissions of the user running HAProxy.