Vendor-Signed UEFI Applications Allow Secure Boot Bypass

CERT/CC disclosed a Secure Boot bypass (VU#457458) discovered by ESET’s Martin Smolar affecting multiple vendor-signed UEFI applications (UEFI shell builds and a GRUB2 module). Vulnerable binaries expose powerful pre-boot functions (memory writes, variable edits, dmpstore) that can be abused to load unsigned code and defeat Secure Boot; vendors are revoking affected binaries via UEFI DBX updates and issuing firmware updates. No public proof-of-concept or confirmed in-the-wild exploitation has been reported, and successful exploitation requires administrative privileges or physical access, but would allow persistent compromise below the operating system.