use auxiliary/scanner/vnc/vnc_none_auth
msf auxiliary(vnc_none_auth) > show options
Module options (auxiliary/scanner/vnc/vnc_none_auth):
Name Current Setting Required Description
---- --------------- -------- -----------
RHOSTS yes The target address range or CIDR identifier
RPORT 5900 yes The target port
THREADS 1 yes The number of concurrent threads
msf auxiliary(vnc_none_auth) > set RHOSTS 192.168.1.129
RHOSTS => 192.168.1.129
msf auxiliary(vnc_none_auth) > set THREADS 50
THREADS => 50
msf auxiliary(vnc_none_auth) > run
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed