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.