The shim package contains a first-stage UEFI boot loader that handles chaining to a trusted full boot loader under secure boot environments. Security Fix: * grub2: acpi command allows privileged user to load crafted ACPI tables when Secure Boot is enabled * grub2: Use-after-free in rmmod command * grub2: Out-of-bounds write in grub_usb_device_initialize * grub2: Stack buffer overflow in grub_parser_split_cmdline * grub2: cutmem command allows privileged user to remove memory regions when Secure Boot is enabled * grub2: Heap out-of-bounds write in short form option parser * grub2: Heap out-of-bounds write due to miscalculation of space required for quoting For more details about the security issue, including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page listed in the References section. Additional Changes: For detailed information on changes in this release, see the Red Hat Enterprise Linux 8.4 Release Notes linked from the References section.