Denial-of-Service in gRPC

There exists an vulnerability causing an abort() to be called in gRPC.  The following headers cause gRPC's C++ implementation to abort() when called via http2: te: x (x != trailers) :scheme: x (x != http, https) grpclb_client_stats: x (x == anything) On top of sending one of those headers, a later header must be sent that gets the total header size past 8KB. We recommend upgrading past git commit 2485fa94bd8a723e5c977d55a3ce10b301b437f8 or v1.53 and above.