GNU GRUB (aka GRUB2) through 2.12 has a heap-based buffer overflow in fs/hfs.c via crafted sblock data in an HFS filesystem.

...

Linux: Mounting of hfsplus filesystems

The hfsplus filesystem type is a hierarchical filesystem designed to replace hfs that allows you to mount Mac OS X filesystems. Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. SPDX-FileCopyrightText:...