Some HTTP/2 implementations are vulnerable to a reset flood, potentially leading to a denial of service.
Servers that accept direct connections from untrusted clients could be remotely made to allocate an unlimited amount of memory, until the program crashes. The attacker opens a number of streams and sends an invalid request over each stream that should solicit a stream of RSTSTREAM frames from the peer. Depending on how the peer queues the RSTSTREAM frames, this can consume excess memory, CPU, or both.