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Gentoo Linux Security Advisory                           GLSA 201512-03
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                                           https://security.gentoo.org/
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 Severity: Normal
    Title: GRUB: Authentication bypass
     Date: December 19, 2015
     Bugs: #568326
       ID: 201512-03

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Synopsis
=======
GRUB's authentication prompt can be bypassed by entering a sequence of
backspace characters.

Background
=========
GNU GRUB is a multiboot boot loader used by most Linux systems.

Affected packages
================
    -------------------------------------------------------------------
     Package              /     Vulnerable     /            Unaffected
    -------------------------------------------------------------------
  1  sys-boot/grub            < 2.02_beta2-r8               *>= 0.97 *
                                                    >= 2.02_beta2-r8 *
    -------------------------------------------------------------------
     NOTE: Packages marked with asterisks require manual intervention!

Description
==========
An integer underflow in GRUB's username/password authentication code
has been discovered.

Impact
=====
An attacker with access to the system console may bypass the username
prompt by entering a sequence of backspace characters, allowing them
e.g. to get full access to GRUB's console or to load a customized
kernel.

Workaround
=========
There is no known workaround at this time.

Resolution
=========
All GRUB 2.x users should upgrade to the latest version:

  # emerge --sync
  # emerge --ask --oneshot --verbose ">=sys-boot/grub-2.02_beta2-r8"

After upgrading, make sure to run the grub2-install command with
options appropriate for your system. See the GRUB2 Quick Start guide in
the references below for examples. Your system will be vulnerable until
this action is performed.

References
=========
[ 1 ] CVE-2015-8370
      http://nvd.nist.gov/nvd.cfm?cvename=CVE-2015-8370
[ 2 ] GRUB2 Quick Start guide
      https://wiki.gentoo.org/wiki/GRUB2_Quick_Start

Availability
===========
This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

 https://security.gentoo.org/glsa/201512-03

Concerns?
========
Security is a primary focus of Gentoo Linux and ensuring the
confidentiality and security of our users' machines is of utmost
importance to us. Any security concerns should be addressed to
security@gentoo.org or alternatively, you may file a bug at
https://bugs.gentoo.org.

License
======
Copyright 2015 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

https://creativecommons.org/licenses/by-sa/2.5/