Ubuntu 18.04 LTS / 20.04 LTS : Linux kernel vulnerabilities (USN-4679-1)

##
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4679-1. The text
# itself is copyright (C) Canonical, Inc. See
# <http://www.ubuntu.com/usn/>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
##

include('compat.inc');

if (description)
{
  script_id(144750);
  script_version("1.9");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/08/29");

  script_cve_id(
    "CVE-2020-25656",
    "CVE-2020-25668",
    "CVE-2020-25704",
    "CVE-2020-27675",
    "CVE-2020-27777",
    "CVE-2020-28974"
  );
  script_xref(name:"USN", value:"4679-1");

  script_name(english:"Ubuntu 18.04 LTS / 20.04 LTS : Linux kernel vulnerabilities (USN-4679-1)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Ubuntu host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The remote Ubuntu 18.04 LTS / 20.04 LTS host has a package installed that is affected by multiple vulnerabilities as
referenced in the USN-4679-1 advisory.

    It was discovered that the console keyboard driver in the Linux kernel contained a race condition. A local
    attacker could use this to expose sensitive information (kernel memory). (CVE-2020-25656)

    Minh Yuan discovered that the tty driver in the Linux kernel contained race conditions when handling
    fonts. A local attacker could possibly use this to expose sensitive information (kernel memory).
    (CVE-2020-25668)

    Kiyin () discovered that the perf subsystem in the Linux kernel did not properly deallocate memory
    in some situations. A privileged attacker could use this to cause a denial of service (kernel memory
    exhaustion). (CVE-2020-25704)

    Jinoh Kang discovered that the Xen event channel infrastructure in the Linux kernel contained a race
    condition. An attacker in guest could possibly use this to cause a denial of service (dom0 crash).
    (CVE-2020-27675)

    Daniel Axtens discovered that PowerPC RTAS implementation in the Linux kernel did not properly restrict
    memory accesses in some situations. A privileged local attacker could use this to arbitrarily modify
    kernel memory, potentially bypassing kernel lockdown restrictions. (CVE-2020-27777)

    Minh Yuan discovered that the framebuffer console driver in the Linux kernel did not properly handle fonts
    in some conditions. A local attacker could use this to cause a denial of service (system crash) or
    possibly expose sensitive information (kernel memory). (CVE-2020-28974)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/notices/USN-4679-1");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2020-27777");
  script_set_attribute(attribute:"cvss3_score_source", value:"CVE-2020-25668");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/10/22");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/01/06");
  script_set_attribute(attribute:"plugin_publication_date", value:"2021/01/06");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1026-raspi");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1031-kvm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1033-gcp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1033-gke");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1034-oracle");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1035-azure");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-59-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-59-generic-lpae");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-59-lowlatency");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Ubuntu Local Security Checks");

  script_copyright(english:"Ubuntu Security Notice (C) 2021-2024 Canonical, Inc. / NASL script (C) 2021-2024 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl", "linux_alt_patch_detect.nasl");
  script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");

  exit(0);
}

include('debian_package.inc');
include('ksplice.inc');

if ( ! get_kb_item('Host/local_checks_enabled') ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_release = get_kb_item('Host/Ubuntu/release');
if ( isnull(os_release) ) audit(AUDIT_OS_NOT, 'Ubuntu');
os_release = chomp(os_release);
if (! ('18.04' >< os_release || '20.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 18.04 / 20.04', 'Ubuntu ' + os_release);
if ( ! get_kb_item('Host/Debian/dpkg-l') ) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);

var kernel_mappings = {
  '18.04': {
    '5.4.0': {
      'generic': '5.4.0-59',
      'generic-lpae': '5.4.0-59',
      'lowlatency': '5.4.0-59',
      'raspi': '5.4.0-1026',
      'gcp': '5.4.0-1033',
      'gke': '5.4.0-1033',
      'oracle': '5.4.0-1034',
      'azure': '5.4.0-1035'
    }
  },
  '20.04': {
    '5.4.0': {
      'generic': '5.4.0-59',
      'generic-lpae': '5.4.0-59',
      'lowlatency': '5.4.0-59',
      'raspi': '5.4.0-1026',
      'kvm': '5.4.0-1031',
      'gcp': '5.4.0-1033',
      'oracle': '5.4.0-1034',
      'azure': '5.4.0-1035'
    }
  }
};

var host_kernel_release = get_kb_item('Host/uptrack-uname-r');
if (empty_or_null(host_kernel_release)) host_kernel_release = get_kb_item_or_exit('Host/uname-r');
var host_kernel_base_version = get_kb_item_or_exit('Host/Debian/kernel-base-version');
var host_kernel_type = get_kb_item_or_exit('Host/Debian/kernel-type');
if(empty_or_null(kernel_mappings[os_release][host_kernel_base_version][host_kernel_type])) audit(AUDIT_INST_VER_NOT_VULN, 'kernel ' + host_kernel_release);

var extra = '';
var kernel_fixed_version = kernel_mappings[os_release][host_kernel_base_version][host_kernel_type] + "-" + host_kernel_type;
if (deb_ver_cmp(ver1:host_kernel_release, ver2:kernel_fixed_version) < 0)
{
  extra += 'Running Kernel level of ' + host_kernel_release + ' does not meet the minimum fixed level of ' + kernel_fixed_version + ' for this advisory.\n\n';
}
  else
{
  audit(AUDIT_PATCH_INSTALLED, 'Kernel package for USN-4679-1');
}

if (get_one_kb_item('Host/ksplice/kernel-cves'))
{
  var cve_list = make_list('CVE-2020-25656', 'CVE-2020-25668', 'CVE-2020-25704', 'CVE-2020-27675', 'CVE-2020-27777', 'CVE-2020-28974');
  if (ksplice_cves_check(cve_list))
  {
    audit(AUDIT_PATCH_INSTALLED, 'KSplice hotfix for USN-4679-1');
  }
  else
  {
    extra = extra + ksplice_reporting_text();
  }
}
if (extra) {
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : extra
  );
  exit(0);
}