A flaw was discovered in the qemu code for temporarily exposing an NBD 
server (used for storage migration and other tasks), where qemu can
crash if a client still has a socket open at the time the server is
taken offline. Even when qemu is set up to only accept clients with
proper TLS credentials, an attacker without the TLS credentials can
exploit the flaw by connecting a second socket while a storage
migration is ongoing through the intended socket, where the attacker
then stalls the NBD handshake to not reach the point of the TLS
negotiation, then waiting for the server to go offline. When the NBD
server is stopped, closing the attacker's socket can cause qemu to
crash, forming a denial of service attack.