Grub2: use-after-free in grub_file_close()

A use-after-free vulnerability has been identified in the GNU GRUB (Grand Unified Bootloader). The flaw occurs because the file-closing process incorrectly retains a memory pointer, leaving an invalid reference to a file system structure. An attacker could exploit this vulnerability to cause grub to crash, leading to a Denial of Service. Possible data integrity or confidentiality compromise is not discarded.