Researchers at firmware security firm Binarly have found six new flaws in U-Boot, the small program that starts up hardware as varied as home routers, smart cameras, and the management chips inside data-center servers.
Four of the bugs can crash a device. The other two could let an attacker who slips a malicious image in front of the bootloader run their own code, before the device has confirmed that the software is genuine.
That last part is the point. A bootloader runs before the operating system, so a flaw here can undermine everything that loads after it. All six bugs are reached while U-Boot is still reading an untrusted image, before it has checked the signature.
What Binarly found
U-Boot can bundle a kernel, device tree, ramdisk, and other boot components into one package, a FIT (Flattened Image Tree), and it checks that package's digital signature before handing over control.
