Asterisk 15.x < 15.7.2 / 16.x < 16.2.1 DoS (AST-2019-001)

2019-03-08T00:00:00
ID ASTERISK_AST_2019_001.NASL
Type nessus
Reporter This script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
Modified 2020-03-02T00:00:00

Description

According to its SIP banner, the version of Asterisk running on the remote host is 15.x prior to 15.7.2, 16.x prior to 16.2.1. It is therefore, affected by an error related to handling SDP traffic and RTP negotiation described in AST-2019-001. This error allows denial of service attacks.

Note that Nessus has not tested for these issues but has instead relied only on the application

                                        
                                            #
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(122670);
  script_version("1.2");
  script_cvs_date("Date: 2019/10/31 15:18:51");

  script_cve_id("CVE-2019-7251");
  script_bugtraq_id(107212);

  script_name(english:"Asterisk 15.x < 15.7.2 / 16.x < 16.2.1 DoS (AST-2019-001)");
  script_summary(english:"Checks the version in the SIP banner.");

  script_set_attribute(attribute:"synopsis", value:
"A telephony application running on the remote host is affected by a
denial of service vulnerability.");
  script_set_attribute(attribute:"description", value:
"According to its SIP banner, the version of Asterisk running on the
remote host is 15.x prior to 15.7.2, 16.x prior to 16.2.1. It is
therefore, affected by an error related to handling SDP traffic and
RTP negotiation described in AST-2019-001. This error allows denial
of service attacks.

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:"http://downloads.asterisk.org/pub/security/AST-2019-001.html");
  script_set_attribute(attribute:"solution", value:
"Upgrade to Asterisk version 15.7.2 / 16.2.1 or later.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:S/C:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2019-7251");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"vuln_publication_date", value:"2019/01/24");
  script_set_attribute(attribute:"patch_publication_date", value:"2019/01/24");
  script_set_attribute(attribute:"plugin_publication_date", value:"2019/03/08");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:digium:asterisk");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("asterisk_detection.nasl");
  script_require_keys("asterisk/sip_detected", "Settings/ParanoidReport");

  exit(0);
}

include("audit.inc");
include("global_settings.inc");
include("misc_func.inc");
include("lists.inc");

get_kb_item_or_exit("asterisk/sip_detected");

asterisk_kbs = get_kb_list_or_exit("sip/asterisk/*/version");

if (report_paranoia < 2) audit(AUDIT_PARANOID);

is_vuln = FALSE;
not_vuln_installs = make_list();
errors = make_list();

foreach kb_name (keys(asterisk_kbs))
{
  vulnerable = 0;

  matches = pregmatch(pattern:"/(udp|tcp)/([0-9]+)/version", string:kb_name);
  if (isnull(matches))
  {
    collib::push("Unexpected error parsing port number from '"+kb_name+"'.", errors);
    continue;
  }

  proto = matches[1];
  port  = matches[2];
  version = asterisk_kbs[kb_name];

  if (version == 'unknown')
  {
    collib::push("Unable to obtain version of installation on " + proto + "/" + port + ".", errors);
    continue;
  }

  banner = get_kb_item("sip/asterisk/" + proto + "/" + port + "/source");
  if (!banner)
  {
    # We have version but banner is missing;
    # log error and use in version-check though.
    collib::push("KB item 'sip/asterisk/" + proto + "/" + port + "/source' is missing.", errors);
    banner = 'unknown';
  }

  if (version =~ "^15([^0-9])" && "cert" >!< tolower(version))
  {
    fixed = "15.7.2";
    vulnerable = ver_compare(ver:version, fix:fixed, app:"asterisk");
  }
  else if (version =~ "^16([^0-9])" && "cert" >!< tolower(version))
  {
    fixed = "16.2.1";
    vulnerable = ver_compare(ver:version, fix:fixed, app:"asterisk");
  }

  if (vulnerable < 0)
  {
    is_vuln = TRUE;
    report =
        '\n  Version source    : ' + banner +
        '\n  Installed version : ' + version +
        '\n  Fixed version     : ' + fixed +
        '\n';
      security_report_v4(severity:SECURITY_WARNING, port:port, proto:proto, extra:report);
  }
  else collib::push(version + " on port " + proto + "/" + port, not_vuln_installs);
}

if (max_index(errors))
{
  if (max_index(errors) == 1) errmsg = errors[0];
  else errmsg = 'Errors were encountered verifying installations : \n  ' + join(errors, sep:'\n  ');

  exit(1, errmsg);
}
else
{
  installs = max_index(not_vuln_installs);
  if (installs == 0)
  {
    if (is_vuln) exit(0);
    else audit(AUDIT_NOT_INST, "Asterisk");
  }
  else audit(AUDIT_INST_VER_NOT_VULN, "Asterisk", not_vuln_installs);
}