Microsoft Office Remote Code Execution Vulnerability (KB4493206)

# Copyright (C) 2021 Greenbone Networks GmbH
# Some text descriptions might be excerpted from (a) referenced
# source(s), and are Copyright (C) by the respective right holder(s).
#
# SPDX-License-Identifier: GPL-2.0-or-later
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.817719");
  script_version("2021-08-25T14:01:09+0000");
  script_cve_id("CVE-2021-28455");
  script_tag(name:"cvss_base", value:"6.5");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:S/C:P/I:P/A:P");
  script_tag(name:"last_modification", value:"2021-08-25 14:01:09 +0000 (Wed, 25 Aug 2021)");
  script_tag(name:"severity_vector", value:"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2021-05-18 16:02:00 +0000 (Tue, 18 May 2021)");
  script_tag(name:"creation_date", value:"2021-05-12 18:37:56 +0530 (Wed, 12 May 2021)");
  script_name("Microsoft Office Remote Code Execution Vulnerability (KB4493206)");

  script_tag(name:"summary", value:"This host is missing an important security
  update according to Microsoft KB4493206");

  script_tag(name:"vuldetect", value:"Checks if a vulnerable version is present
  on the target host.");

  script_tag(name:"insight", value:"A remote code execution vulnerability exists
  in Microsoft Office software when it fails to properly handle a specially
  crafted Office file.");

  script_tag(name:"impact", value:"Successful exploitation will allow an attacker
  to execute arbitrary code in the context of the current user.");

  script_tag(name:"affected", value:"Microsoft Office 2013 Service Pack 1.");

  script_tag(name:"solution", value:"The vendor has released updates. Please see the references for more information.");

  script_tag(name:"solution_type", value:"VendorFix");
  script_tag(name:"qod_type", value:"executable_version");
  script_xref(name:"URL", value:"https://support.microsoft.com/en-us/help/4493206");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2021 Greenbone Networks GmbH");
  script_family("Windows : Microsoft Bulletins");
  script_dependencies("secpod_office_products_version_900032.nasl");
  script_mandatory_keys("MS/Office/Ver");
  script_require_ports(139, 445);
  exit(0);
}

include("smb_nt.inc");
include("host_details.inc");
include("version_func.inc");
include("secpod_smb_func.inc");

officeVer = get_kb_item("MS/Office/Ver");
if(!officeVer|| officeVer !~ "^15\."){
  exit(0);
}

if(!os_arch = get_kb_item("SMB/Windows/Arch")){
  exit(0);
}

if("x86" >< os_arch){
  key_list = make_list("SOFTWARE\Microsoft\Windows\CurrentVersion");
}
else if("x64" >< os_arch){
  key_list =  make_list("SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion",
                        "SOFTWARE\Microsoft\Windows\CurrentVersion");
}

foreach key(key_list)
{
  msPath = registry_get_sz(key:key, item:"CommonFilesDir");
  if(msPath)
  {
    offPath = msPath + "\Microsoft Shared\Office15";
    msdllVer = fetch_file_version(sysPath:offPath, file_name:"acecore.dll");

    if(msdllVer && msdllVer =~ "^15\.")
    {
      if(version_is_less(version:msdllVer, test_version:"15.0.5345.1001"))
      {
        report = report_fixed_ver( file_checked:offPath + "\acecore.dll",
                                   file_version:msdllVer, vulnerable_range:"15.0 - 15.0.5345.1000");
        security_message(data:report);
        exit(0);
      }
    }
  }
}
exit(0);