This indicates an attack attempt against a denial-of-service vulnerability in the Grandstream BudgeTone 200 IP phone.
The vulnerability is due to the device's inability to properly handle certain malformed messages. Remote attackers may exploit this to cause the device to crash or reboot, denying service to legitimate users.
Grandstream BudgeTone 200 (BT−200) version 18.104.22.168 and prior.
Denial of service
We are not aware of any officially supplied patch for this issue as of this writing.