(RHSA-2015:2623) Moderate: grub2 security and bug fix update

The grub2 packages provide version 2 of the Grand Unified Bootloader
(GRUB), a highly configurable and customizable bootloader with modular
architecture. The packages support a variety of kernel formats, file
systems, computer architectures, and hardware devices.

A flaw was found in the way the grub2 handled backspace characters entered
in username and password prompts. An attacker with access to the system
console could use this flaw to bypass grub2 password protection and gain
administrative access to the system. (CVE-2015-8370)

This update also fixes the following bug:

• When upgrading from Red Hat Enterprise Linux 7.1 and earlier, a
  configured boot password was not correctly migrated to the newly introduced
  user.cfg configuration files. This could possibly prevent system
  administrators from changing grub2 configuration during system boot even if
  they provided the correct password. This update corrects the password
  migration script and the incorrectly generated user.cfg file. (BZ#1290089)

All grub2 users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. For this update to take
effect on BIOS-based machines, grub2 needs to be reinstalled as documented
in the “Reinstalling GRUB 2 on BIOS-Based Machines” section of the Red Hat
Enterprise Linux 7 System Administrator’s Guide linked to in the References
section. No manual action is needed on UEFI-based machines.