Grandstream GXP-2000 VoIP Desktop Phone firmware version 1.1.0.5 allows remote attackers to cause a denial of service (hang or reboot) via a large amount of ASCII data sent to port (1) 5060/UDP (2) 5062/UDP (3) 5064/UDP (4) 5066/UDP (5) 9876/UDP or (6) 26789/UDP.