If it's got a full general purpose CPU and OS, yeah it can be vulnerable, but a lot of IoT stuff use microcontrollers that run one monolithic program. There's usually no other OS services or hidden exploits to use, I'm having trouble imagining how you'd break out of such a device once you've taken control of it, if you can at all. Can a smarter person correct me if I'm wrong, and explain how chips like the common ESP32 and ESP8266 are vulnerable to attack? Maybe through the RTOS and Wifi stack?
I'm an embedded hobbyist so I'd like to learn about securing my own devices.