Load balancers enable efficient use of network resources by distributing traffic fairly across them. In software-defined networking (SDN), load balancing is most often realized by a controller application that solicits traffic load reports from network switches and enforces load balancing decisions through flow rules. This separation between the control and data planes in SDNs creates an opportunity for an adversary at a compromised switch to misreport traffic loads to influence load balancing. In this paper, we evaluate the ability of such an adversary to control the volume of traffic flowing through a compromised switch by misreporting traffic loads. We use a queuing theoretic approach to model the attack and develop algorithms for misreporting that allow an adversary to tune attack parameters toward specific adversarial goals. We validate the algorithms with a virtual network testbed, finding that through misreporting the adversary can draw nearly all of the load in the subnetwork (+750%, or 85% of the load in the system), or an adversary-desired amount of load (a target load, e.g., +200%) to within 12% error of that target. This is yet another example of how depending on untrustworthy reporting in making control decisions can lead to fundamental security failures.