ISC BIND DoS Vulnerability (CVE-2020-8621) - Linux

# Copyright (C) 2020 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.

CPE = "cpe:/a:isc:bind";

if (description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.144437");
  script_version("2021-07-07T11:00:41+0000");
  script_tag(name:"last_modification", value:"2021-07-07 11:00:41 +0000 (Wed, 07 Jul 2021)");
  script_tag(name:"creation_date", value:"2020-08-21 03:14:56 +0000 (Fri, 21 Aug 2020)");
  script_tag(name:"cvss_base", value:"4.3");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:M/Au:N/C:N/I:N/A:P");
  script_tag(name:"severity_vector", value:"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2020-10-20 12:15:00 +0000 (Tue, 20 Oct 2020)");

  script_cve_id("CVE-2020-8621");

  script_tag(name:"qod_type", value:"remote_banner_unreliable");

  script_tag(name:"solution_type", value:"VendorFix");

  script_name("ISC BIND DoS Vulnerability (CVE-2020-8621) - Linux");

  script_category(ACT_GATHER_INFO);

  script_copyright("Copyright (C) 2020 Greenbone Networks GmbH");
  script_family("Denial of Service");
  script_dependencies("gb_isc_bind_consolidation.nasl", "os_detection.nasl");
  script_mandatory_keys("isc/bind/detected", "Host/runs_unixoide");

  script_tag(name:"summary", value:"ISC BIND is prone to a denial of service vulnerability.");

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

  script_tag(name:"insight", value:"While query forwarding and QNAME minimization are mutually incompatible, BIND
  did sometimes allow QNAME minimization when continuing with recursion after 'forward first' did not result in an
  answer. In these cases the data used by QNAME minimization might be inconsistent, leading to an assertion failure
  causing the server to exit.");

  script_tag(name:"impact", value:"If a server is configured with both QNAME minimization and 'forward first' then
  an attacker who can send queries to it may be able to trigger the condition that will cause the server to crash.

  Servers that 'forward only' are not affected.");

  script_tag(name:"affected", value:"BIND 9.14.0 - 9.16.5 and 9.17.0 - 9.17.3.");

  script_tag(name:"solution", value:"Update to version 9.16.6, 9.17.4 or later.");

  script_xref(name:"URL", value:"https://kb.isc.org/docs/cve-2020-8621");

  exit(0);
}

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

if (isnull(port = get_app_port(cpe: CPE)))
  exit(0);

if (!infos = get_app_full(cpe: CPE, port: port, exit_no_version: TRUE))
  exit(0);

version = infos["version"];
proto = infos["proto"];
location = infos["location"];

if (version_in_range(version: version, test_version: "9.14.0", test_version2: "9.16.5")) {
  report = report_fixed_ver(installed_version: version, fixed_version: "9.16.6", install_path: location);
  security_message(port: port, data: report, proto: proto);
  exit(0);
}

if (version_in_range(version: version, test_version: "9.17.0", test_version2: "9.17.3")) {
  report = report_fixed_ver(installed_version: version, fixed_version: "9.17.4", install_path: location);
  security_message(port: port, data: report, proto: proto);
  exit(0);
}

exit(99);