It is possible for a malicious or malfunctioning client to send less
than the expected amount of data to the server. If this happens, the
server will hang indefinitely waiting for the remainder (or until the
connection gets closed). Because iperf3 is deliberately designed to
service only one client connection at a time, this will prevent other
connections to the iperf3 server.
Avoid running iperf3 with root privileges to minimize impact.
Update iperf3 to a version containing the fix (i.e. iperf-3.15 or
later).