Similar to the bulb bug, a malformed Zigbee frame renders the gateway unresponsive so that it can't control the connected lights and other devices via the Ikea Home Smart app.
That doesn't sound too different to how unhacked Ikea Trådfri are to be honest.
I bought some as an experiment as you can only use the app if you're local to the controller, they didn't need stuff hosted in the Cloud to work and they were cheap.
The lightbulbs seem to love ignoring their controller and then need to be re-added. I also needed to re-link the app to the controller a few times too.
They're also "fun" if your network has multiple VLANs, in the end the only way I got them to work was by setting the port to only have a single VLAN on it. I have a vague memory of setting a fixed IP address too.