CentOS 7 : grub2 (CESA-2015:2623)

2015-12-17T00:00:00
ID CENTOS_RHSA-2015-2623.NASL
Type nessus
Reporter Tenable
Modified 2016-04-28T00:00:00

Description

Updated grub2 packages that fix one security issue and one bug are now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Moderate security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available from the CVE link in the References section.

[Updated 27 January 2016] This advisory has been updated to document additional steps that need to be performed on BIOS-based systems after installing this update. No changes were made to the packages included in the advisory.

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.

                                        
                                            #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from Red Hat Security Advisory RHSA-2015:2623 and 
# CentOS Errata and Security Advisory 2015:2623 respectively.
#

include("compat.inc");

if (description)
{
  script_id(87422);
  script_version("$Revision: 2.4 $");
  script_cvs_date("$Date: 2016/04/28 18:15:07 $");

  script_cve_id("CVE-2015-8370");
  script_osvdb_id(131484);
  script_xref(name:"RHSA", value:"2015:2623");

  script_name(english:"CentOS 7 : grub2 (CESA-2015:2623)");
  script_summary(english:"Checks rpm output for the updated packages");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote CentOS host is missing one or more security updates."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"Updated grub2 packages that fix one security issue and one bug are now
available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Moderate
security impact. A Common Vulnerability Scoring System (CVSS) base
score, which gives a detailed severity rating, is available from the
CVE link in the References section.

[Updated 27 January 2016] This advisory has been updated to document
additional steps that need to be performed on BIOS-based systems after
installing this update. No changes were made to the packages included
in the advisory.

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."
  );
  # http://lists.centos.org/pipermail/centos-announce/2015-December/021545.html
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?aa464242"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Update the affected grub2 packages."
  );
  script_set_cvss_base_vector("CVSS2#AV:L/AC:M/Au:N/C:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:ND/RC:C");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:grub2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:grub2-efi");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:grub2-efi-modules");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:grub2-tools");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:centos:centos:7");

  script_set_attribute(attribute:"patch_publication_date", value:"2015/12/15");
  script_set_attribute(attribute:"plugin_publication_date", value:"2015/12/17");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2015-2016 Tenable Network Security, Inc.");
  script_family(english:"CentOS Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/CentOS/release", "Host/CentOS/rpm-list");

  exit(0);
}


include("audit.inc");
include("global_settings.inc");
include("rpm.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/CentOS/release")) audit(AUDIT_OS_NOT, "CentOS");
if (!get_kb_item("Host/CentOS/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);


cpu = get_kb_item("Host/cpu");
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "CentOS", cpu);


flag = 0;
if (rpm_check(release:"CentOS-7", cpu:"x86_64", reference:"grub2-2.02-0.33.el7.centos.1")) flag++;
if (rpm_check(release:"CentOS-7", cpu:"x86_64", reference:"grub2-efi-2.02-0.33.el7.centos.1")) flag++;
if (rpm_check(release:"CentOS-7", cpu:"x86_64", reference:"grub2-efi-modules-2.02-0.33.el7.centos.1")) flag++;
if (rpm_check(release:"CentOS-7", cpu:"x86_64", reference:"grub2-tools-2.02-0.33.el7.centos.1")) flag++;


if (flag)
{
  if (report_verbosity > 0) security_warning(port:0, extra:rpm_report_get());
  else security_warning(0);
  exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");