phpIPAM through 1.8.1 fails to verify that a requested IP address belongs to the subnet a temporary share token was issued for. In app/temp_share/index.php and app/temp_share/address.php, when the share type is 'subnets', the subnetId parameter is used directly as a database primary key to fetch an address without confirming the address belongs to the authorized subnet. An unauthenticated party holding any valid, non-expired temporary share URL can enumerate the subnetId parameter to read every IP address record across all sections and subnets, including hostnames, DNS names, MAC addresses, owner/contact fields, and notes (which may contain credentials and configuration details).