Adjacent network access means reaching a device from a nearby network position rather than from the public internet. The attacker may be on the same Wi-Fi, the same local subnet, a Bluetooth range, a vehicle network, or another reachable segment close to the target. This is different from remote internet access, because the attacker often needs physical proximity or a foothold in the local environment.
In cyber security, adjacent access matters because many embedded devices trust local traffic too much. A web admin panel, update service, or pairing interface may be exposed only to nearby clients, yet still allow configuration changes, data theft, or even code execution if authentication or session handling is weak. Defenders reduce this risk by segmenting networks, disabling unnecessary radios and services, using strong authentication, and treating local interfaces as attack surfaces, not safe zones.