Plex Media Server < 1.21.3.4014 SSDP (PMSSDP) Reflection/Amplification DDoS Attack

# 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("1.3.6.1.4.1.25623.1.0.145346");
  script_version("2021-09-29T05:25:13+0000");
  script_tag(name:"last_modification", value:"2021-09-29 05:25:13 +0000 (Wed, 29 Sep 2021)");
  script_tag(name:"creation_date", value:"2021-02-10 07:17:59 +0000 (Wed, 10 Feb 2021)");
  script_tag(name:"cvss_base", value:"5.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:P");

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

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

  script_name("Plex Media Server < 1.21.3.4014 SSDP (PMSSDP) Reflection/Amplification DDoS Attack");

  script_category(ACT_GATHER_INFO);

  script_copyright("Copyright (C) 2021 Greenbone Networks GmbH");
  script_family("Denial of Service");
  script_dependencies("global_settings.nasl");
  script_require_udp_ports(32410, 32412, 32413, 32414);
  script_mandatory_keys("keys/is_public_addr");

  script_tag(name:"summary", value:"Plex Media Server installations in a specific (and uncommon)
  network position could potentially be used to reflect UDP traffic on certain device-discovery
  ports as part of a possible DDoS (distributed denial-of-service) attack.");

  script_tag(name:"insight", value:"Plex Media Server instances which have either been deployed on a
  public-facing network DMZ or in an Internet Data Center (IDC), or with manually configured
  port-forwarding rules which forward specific UDP ports from the public Internet to devices running
  Plex Media Server, can potentially be abused as part of possible DDoS attacks.

  These actions can have the effect of exposing a Plex UPnP-enabled service registration responder
  to the general Internet, where it can be abused to generate reflection/amplification DDoS
  attacks.");

  script_tag(name:"vuldetect", value:"Sends a crafted UDP request and checks the response.

  Note:

  This VT is only reporting a vulnerability if the target system / service is accessible from a
  public WAN (Internet) / public LAN.

  A configuration option 'Network type' to define if a scanned network should be seen as a public
  LAN can be found in the preferences of the following VT:

  Global variable settings (OID: 1.3.6.1.4.1.25623.1.0.12288)");

  script_tag(name:"affected", value:"Plex Media Server prior to version 1.21.3.4014.");

  script_tag(name:"solution", value:"Update to version 1.21.3.4014 or later. For mitigation steps
  see the referenced vendor response.");

  script_xref(name:"URL", value:"https://forums.plex.tv/t/security-regarding-ssdp-reflection-amplification-ddos/687162");
  script_xref(name:"URL", value:"https://www.netscout.com/blog/asert/plex-media-ssdp-pmssdp-reflectionamplification-ddos-attack");
  script_xref(name:"URL", value:"https://mp.weixin.qq.com/s/y8IqT_mT-oC4EVC4y3bVSw");

  exit(0);
}

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

if (!is_public_addr())
  exit(0);

port_list = make_list(32410, 32412, 32413, 32414);

request = "M-SEARCH * HTTP/1.1";
req_len = strlen(request);

foreach port (port_list) {
  if (!get_udp_port_state(port))
    continue;

  soc = open_sock_udp(port);
  if (!soc)
    continue;

  send(socket: soc, data: request);
  res = recv(socket: soc, length: 4096);
  close(soc);

  if (!res || res !~ "^HTTP/1\.[01] 200")
    continue;

  res_len = strlen(res);

  if (res_len > (10 * req_len)) {
    report = 'We have sent a request of ' + req_len + ' bytes and received a response of ' + res_len + ' bytes.';
    security_message(port: port, data: report, proto: "udp");
    exit(0);
  }
}

exit(99);