A reachable assertion in Apache bRPC (version < 1.18.0) on all platforms allows a malicious remote peer to crash the process, resulting in denial of service. Root Cause: When a Socket with health checking enabled fails, Socket::WaitAndReset closes its file descriptor while the event dispatcher may still be delivering an input event (EPOLLIN/EVFILT_READ) that was fetched for the just-closed fd. If the health check then succeeds and revives the Socket, Socket::Address succeeds again while the fd is still -1 (the next write reconnects on demand). In that window, Socket::OnInputEvent hits CHECK(!(events & EPOLLIN)) (or the kqueue equivalent) because the Socket is addressable but has no fd. CHECK failures terminate the process when bRPC is built with glog or when the gflag -crash_on_fatal_log…