A flaw was found in iperf, a utility for testing network performance using TCP, UDP, and SCTP. A malicious or malfunctioning client can send less than the expected amount of data to the iperf server, which can cause the server to hang indefinitely waiting for the remainder or until the connection gets closed. This will prevent other connections to the server, leading to a denial of service.
The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are explicitly allowed by policy because the inputs are assumed to be safe, but the list is too permissive - that is, it allows an input that is unsafe, leading to resultant weaknesses.