Impact

On arm64 and riscv64, systemd-boot allows a local user to specify a device tree blob and loads it, even when secure boot mode is enabled when using type #1 BLS setups. DTBs are loaded and parsed by the kernel before ExitBootServices(), and the kernel itself disallows loading DTBs via the dtb= kernel command line option when secure boot is enabled.

This feature was introduced in v250 by: 6e86342bb82

As far as we are aware, there are no Shim-trusted arm64/riscv64 systemd-boot binaries published anywhere, so the severity and impact are low, as it affects only local self-signed secure boot deployments of systemd-boot on arm64/riscv64.

Patches

Fixed in main and 254.4 253.11 252.17 251.19 250.13

#29228
systemd/systemd-stable#324
systemd/systemd-stable#325
systemd/systemd-stable#326
systemd/systemd-stable#327
systemd/systemd-stable#328

Workarounds

Use type #2 BLS setups

References

#29228