So you need to 1) Have a server which boots from PXE, 2) Have it do PXE on the same interface used for connections to the internet, 3) Lack a firewall filtering out unexpected or malformed ICMP packages(?), and 4) Do it at the exact moment the physical server is rebooting.
Seems like it is basically zero attack surface when it comes to remotely compromising a server. A client device, on the other hand, would be way easier to exploit, and being able to fool Secure Boot would be very interesting to people trying to bypass DRM or cheat in video games, and of course Evil Maids and security agencies.
If you're on the same LAN segment, you can probably see the DHCPDISCOVER messages that the UEFI would send as part of the PXE boot process. I would guess that you could also tell the difference between a DHCP request from UEFI vs one from Linux/Windows.
Given, without any network level DHCP guard configuration, you could likely also send your own DHCPOFFER and just tell it to PXE-boot your own image :) I suppose for some trusted-boot threat scenarios code execution at the UEFI level is a bigger issue. No idea how modern UEFI PXE-boot deals with signed images.
For client devices who PXE boot (rare) and also are on Ethernet during boot (basically desktops and docked laptops) and also reachable by pings (so the attacker needs to be inside the network).
Some networks carry ICMP through untouched. Why you'd be using public addresses for your systems between DHCP and PXE boot is beyond me, but it's possible. However, someone would need to spray and pray because they wouldn't have visibility within the network to know about the DHCP and PXE traffic actually happening at that time.
So you need to 1) Have a server which boots from PXE, 2) Have it do PXE on the same interface used for connections to the internet, 3) Lack a firewall filtering out unexpected or malformed ICMP packages(?), and 4) Do it at the exact moment the physical server is rebooting.
Seems like it is basically zero attack surface when it comes to remotely compromising a server. A client device, on the other hand, would be way easier to exploit, and being able to fool Secure Boot would be very interesting to people trying to bypass DRM or cheat in video games, and of course Evil Maids and security agencies.