OpenSSH < 7.2 Untrusted X11 Forwarding Fallback Security Bypass

#
# (C) Tenable, Inc.
#

include("compat.inc");

if (description)
{
  script_id(90022);
  script_version("1.10");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/03/27");

  script_cve_id("CVE-2016-1908");

  script_name(english:"OpenSSH < 7.2 Untrusted X11 Forwarding Fallback Security Bypass");
  script_summary(english:"Checks the OpenSSH banner version.");

  script_set_attribute(attribute:"synopsis", value:
"The SSH server running on the remote host is affected by a security
bypass vulnerability.");
  script_set_attribute(attribute:"description", value:
"According to its banner, the version of OpenSSH running on the remote
host is prior to 7.2. It is, therefore, affected by a security bypass
vulnerability due to a flaw in ssh(1) that is triggered when it falls
back from untrusted X11 forwarding to trusted forwarding when the
SECURITY extension is disabled by the X server. This can result in
untrusted X11 connections that can be exploited by a remote attacker.");
  script_set_attribute(attribute:"see_also", value:"http://www.openssh.com/txt/release-7.2");
  script_set_attribute(attribute:"solution", value:
"Upgrade to OpenSSH version 7.2 or later.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/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:N/UI:N/S:U/C:H/I:H/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-2016-1908");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2016/02/29");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/02/29");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/03/18");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:openbsd:openssh");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2023-2024 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("openssh_detect.nbin");
  script_require_keys("installed_sw/OpenSSH");
  script_require_ports("Services/ssh", 22);

  exit(0);
}

include('backport.inc');
include('vcf.inc');
include('vcf_extras.inc');

var port = get_service(svc:'ssh', default:22, exit_on_fail:TRUE);
var app_info = vcf::openssh::get_app_info(app:'OpenSSH', port:port);

vcf::check_all_backporting(app_info:app_info);

var constraints = [
  {'fixed_version' : '7.2' }
];

vcf::openssh::check_version_and_report(app_info:app_info, constraints:constraints, severity:SECURITY_HOLE);