Denial of Service attack when the switch rejects receiving packets from the controller. This vulnerability affects OpenDaylight's odl-l2switch-switch, which is the feature responsible for the OpenFlow communication. 

From thesis: https://aaltodoc.aalto.fi/bitstream/handle/123456789/21584/master_Bidaj_Andi_2016.pdf?sequence=1
Vulnerability 1: The exploit connects to the OpenDaylight controller running in localhost, port 6653, and sends 100 000 OpenFlow hello packets. Afterwards, the sender closes the stream. The controller tries to send a hello packet for each connection, but the malicious script does not receive any data because stream.recv() is missing. The thread that manages the connection with the exploit does not terminate immediately after the stream is closed. As a result, the number of threads of the controller process grows exponentially until it reaches the maximum number of threads allowed in the running machine (around 32000 threads in our case). Subsequently, the controller crashes.