Ubuntu 16.04 LTS / 18.04 LTS : Linux kernel vulnerabilities (USN-4916-1)

##
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4916-1. The text
# itself is copyright (C) Canonical, Inc. See
# <https://ubuntu.com/security/notices>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
##

include('compat.inc');

if (description)
{
  script_id(148691);
  script_version("1.11");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/01/09");

  script_cve_id("CVE-2021-3493", "CVE-2021-29154");
  script_xref(name:"USN", value:"4916-1");
  script_xref(name:"CISA-KNOWN-EXPLOITED", value:"2022/11/10");

  script_name(english:"Ubuntu 16.04 LTS / 18.04 LTS : Linux kernel vulnerabilities (USN-4916-1)");

  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 16.04 LTS / 18.04 LTS host has a package installed that is affected by multiple vulnerabilities as
referenced in the USN-4916-1 advisory.

  - BPF JIT compilers in the Linux kernel through 5.11.12 have incorrect computation of branch displacements,
    allowing them to execute arbitrary code within the kernel context. This affects
    arch/x86/net/bpf_jit_comp.c and arch/x86/net/bpf_jit_comp32.c. (CVE-2021-29154)

  - The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces
    the setting of file capabilities on files in an underlying file system. Due to the combination of
    unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay
    mounts, an attacker could use this to gain elevated privileges. (CVE-2021-3493)

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-4916-1");
  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:H/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:H/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-3493");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"exploit_framework_core", value:"true");
  script_set_attribute(attribute:"exploited_by_malware", value:"true");
  script_set_attribute(attribute:"metasploit_name", value:'2021 Ubuntu Overlayfs LPE');
  script_set_attribute(attribute:"exploit_framework_metasploit", value:"true");
  script_set_attribute(attribute:"exploit_framework_canvas", value:"true");
  script_set_attribute(attribute:"canvas_package", value:"CANVAS");

  script_set_attribute(attribute:"vuln_publication_date", value:"2021/04/08");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/04/15");
  script_set_attribute(attribute:"plugin_publication_date", value:"2021/04/16");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1017-dell300x");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1070-oracle");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1084-raspi2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1090-kvm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1098-gcp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1099-aws");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1101-snapdragon");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-1113-azure");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-142-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-142-generic-lpae");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.15.0-142-lowlatency");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-1092-kvm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-1127-aws");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-1151-raspi2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-1155-snapdragon");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-209-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-209-generic-lpae");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-209-lowlatency");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-209-powerpc-e500mc");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-209-powerpc-smp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-209-powerpc64-emb");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-4.4.0-209-powerpc64-smp");
  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 (! ('16.04' >< os_release || '18.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 16.04 / 18.04', '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 = {
  '16.04': {
    '4.15.0': {
      'generic': '4.15.0-142',
      'generic-lpae': '4.15.0-142',
      'lowlatency': '4.15.0-142',
      'oracle': '4.15.0-1070',
      'gcp': '4.15.0-1098',
      'aws': '4.15.0-1099',
      'azure': '4.15.0-1113'
    },
    '4.4.0': {
      'generic': '4.4.0-209',
      'generic-lpae': '4.4.0-209',
      'lowlatency': '4.4.0-209',
      'powerpc-e500mc': '4.4.0-209',
      'powerpc-smp': '4.4.0-209',
      'powerpc64-emb': '4.4.0-209',
      'powerpc64-smp': '4.4.0-209',
      'kvm': '4.4.0-1092',
      'aws': '4.4.0-1127',
      'raspi2': '4.4.0-1151',
      'snapdragon': '4.4.0-1155'
    }
  },
  '18.04': {
    '4.15.0': {
      'generic': '4.15.0-142',
      'generic-lpae': '4.15.0-142',
      'lowlatency': '4.15.0-142',
      'dell300x': '4.15.0-1017',
      'oracle': '4.15.0-1070',
      'raspi2': '4.15.0-1084',
      'kvm': '4.15.0-1090',
      'gcp': '4.15.0-1098',
      'aws': '4.15.0-1099',
      'snapdragon': '4.15.0-1101',
      'azure': '4.15.0-1113'
    }
  }
};

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 = 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-4916-1');
}

if (get_one_kb_item('Host/ksplice/kernel-cves'))
{
  var cve_list = make_list('CVE-2021-3493', 'CVE-2021-29154');
  if (ksplice_cves_check(cve_list))
  {
    audit(AUDIT_PATCH_INSTALLED, 'KSplice hotfix for USN-4916-1');
  }
  else
  {
    extra = extra + ksplice_reporting_text();
  }
}
if (extra) {
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : extra
  );
  exit(0);
}