Since the firmware update is not validated, an attacker can install modified firmware on the device. This has a high impact on the availabilty, integrity and confidentiality up to the complete compromise of the device.
Exploitability
AV:NAC:LPR:LUI:NScope
S:UImpact
C:HI:HA:H8.8/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOther