Vulnerabilities > CVE-2016-7407 - Improper Input Validation vulnerability in Dropbear SSH Project Dropbear SSH

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from the FreeBSD VuXML database :
#
# Copyright 2003-2018 Jacques Vidrine and contributors
#
# Redistribution and use in source (VuXML) and 'compiled' forms (SGML,
# HTML, PDF, PostScript, RTF and so forth) with or without modification,
# are permitted provided that the following conditions are met:
# 1. Redistributions of source code (VuXML) must retain the above
#    copyright notice, this list of conditions and the following
#    disclaimer as the first lines of this file unmodified.
# 2. Redistributions in compiled form (transformed to other DTDs,
#    published online in any format, converted to PDF, PostScript,
#    RTF and other formats) must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer
#    in the documentation and/or other materials provided with the
#    distribution.
# 
# THIS DOCUMENTATION IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
# OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
# OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
# BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
# OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS DOCUMENTATION,
# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

include("compat.inc");

if (description)
{
  script_id(93552);
  script_version("2.4");
  script_cvs_date("Date: 2018/11/23 12:49:57");

  script_cve_id("CVE-2016-7406", "CVE-2016-7407", "CVE-2016-7408", "CVE-2016-7409");

  script_name(english:"FreeBSD : dropbear -- multiple vulnerabilities (bc19dcca-7b13-11e6-b99e-589cfc0654e1)");
  script_summary(english:"Checks for updated package in pkg_info output");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote FreeBSD host is missing a security-related update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"Matt Johnston reports :

If specific usernames including '%' symbols can be created on a system
(validated by getpwnam()) then an attacker could run arbitrary code as
root when connecting to Dropbear server.

A dbclient user who can control username or host arguments could
potentially run arbitrary code as the dbclient user. This could be a
problem if scripts or webpages pass untrusted input to the dbclient
program.

dropbearconvert import of OpenSSH keys could run arbitrary code as the
local dropbearconvert user when parsing malicious key files.

dbclient could run arbitrary code as the local dbclient user if
particular -m or -c arguments are provided. This could be an issue
where dbclient is used in scripts.

dbclient or dropbear server could expose process memory to the running
user if compiled with DEBUG_TRACE and running with -v"
  );
  # http://www.openwall.com/lists/oss-security/2016/09/15/2
  script_set_attribute(
    attribute:"see_also",
    value:"https://www.openwall.com/lists/oss-security/2016/09/15/2"
  );
  # https://vuxml.freebsd.org/freebsd/bc19dcca-7b13-11e6-b99e-589cfc0654e1.html
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?002ecf86"
  );
  script_set_attribute(attribute:"solution", value:"Update the affected package.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A: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_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:freebsd:freebsd:dropbear");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:freebsd:freebsd");

  script_set_attribute(attribute:"vuln_publication_date", value:"2016/07/12");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/09/15");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/09/16");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2016-2018 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"FreeBSD Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/FreeBSD/release", "Host/FreeBSD/pkg_info");

  exit(0);
}


include("audit.inc");
include("freebsd_package.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/FreeBSD/release")) audit(AUDIT_OS_NOT, "FreeBSD");
if (!get_kb_item("Host/FreeBSD/pkg_info")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;

if (pkg_test(save_report:TRUE, pkg:"dropbear<2016.74")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:pkg_report_get());
  else security_hole(0);
  exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");

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

include("compat.inc");

if (description)
{
  script_id(93650);
  script_version("1.5");
  script_cvs_date("Date: 2019/11/14");

  script_cve_id(
    "CVE-2016-7406",
    "CVE-2016-7407",
    "CVE-2016-7408",
    "CVE-2016-7409"
  );
  script_bugtraq_id(
    92970,
    92972,
    92973,
    92974
  );

  script_name(english:"Dropbear SSH Server < 2016.72 Multiple Vulnerabilities");
  script_summary(english:"Checks the remote SSH server type and version.");

  script_set_attribute(attribute:"synopsis", value:
"The SSH service running on the remote host is affected by multiple
vulnerabilities.");
  script_set_attribute(attribute:"description", value:
"According to its self-reported version in its banner, Dropbear SSH
running on the remote host is prior to 2016.74. It is, therefore,
affected by the following vulnerabilities :

  - A format string flaw exists due to improper handling of
    string format specifiers (e.g., %s and %x) in usernames
    and host arguments. An unauthenticated, remote attacker
    can exploit this to execute arbitrary code with root
    privileges. (CVE-2016-7406)

  - A flaw exists in dropbearconvert due to improper
    handling of specially crafted OpenSSH key files. An
    unauthenticated, remote attacker can exploit this to
    execute arbitrary code. (CVE-2016-7407)

  - A flaw exists in dbclient when handling the -m or -c
    arguments in scripts. An unauthenticated, remote attacker
    can exploit this, via a specially crafted script, to
    execute arbitrary code. (CVE-2016-7408)

  - A flaw exists in dbclient or dropbear server if they are
    compiled with the DEBUG_TRACE option and then run using
    the -v switch. A local attacker can exploit this to
    disclose process memory. (CVE-2016-7409)");
  script_set_attribute(attribute:"see_also", value:"https://matt.ucc.asn.au/dropbear/CHANGES");
  script_set_attribute(attribute:"solution", value:
"Upgrade to Dropbear SSH version 2016.74 or later.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C");
  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-2016-7407");

  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:"2016/07/21");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/07/21");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/09/22");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:matt_johnston:dropbear_ssh_server");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_detect.nasl");
  script_require_ports("Services/ssh", 22);

  exit(0);
}

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

app         = "Dropbear SSH";
port        = get_service(svc:"ssh", exit_on_fail:TRUE);
orig_banner = get_kb_item_or_exit("SSH/banner/" + port);
banner      = get_backport_banner(banner:orig_banner);

if ("dropbear" >!< banner) audit(AUDIT_NOT_DETECT, app, port);
if (backported) audit(AUDIT_BACKPORT_SERVICE, port, app);

item = eregmatch(pattern:"dropbear_([0-9]+\.[0-9]+(\.[0-9]+)?)($|[^0-9])", string:banner);
if (!item) audit(AUDIT_SERVICE_VER_FAIL, app, port);
version = item[1];

#SSH version : SSH-2.0-dropbear_0.53.1
#SSH version : SSH-2.0-dropbear_2011.54
if (
  # Early
  version =~ "^0\."
  ||
  # 2000-2015
  version =~ "^20(0\d|1[1-5])\."
  ||
  # 2016.0-2016.73
  version =~ "^2016\.([0-6]\d|7[0-3])"
)
{
  report_items = make_array(
    "Version source", orig_banner,
    "Installed version", version,
    "Fixed version", "2016.74"
  );
  order = make_list("Version source", "Installed version", "Fixed version");
  report = report_items_str(report_items:report_items, ordered_fields:order);
  security_report_v4(severity:SECURITY_HOLE, port:port, extra:report);
}
else audit(AUDIT_LISTEN_NOT_VULN, app, port, version);

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Gentoo Linux Security Advisory GLSA 201702-23.
#
# The advisory text is Copyright (C) 2001-2017 Gentoo Foundation, Inc.
# and licensed under the Creative Commons - Attribution / Share Alike 
# license. See http://creativecommons.org/licenses/by-sa/3.0/
#

include("compat.inc");

if (description)
{
  script_id(97266);
  script_version("$Revision: 3.2 $");
  script_cvs_date("$Date: 2017/03/06 14:38:26 $");

  script_cve_id("CVE-2016-7406", "CVE-2016-7407", "CVE-2016-7408", "CVE-2016-7409");
  script_xref(name:"GLSA", value:"201702-23");

  script_name(english:"GLSA-201702-23 : Dropbear: Multiple vulnerabilities");
  script_summary(english:"Checks for updated package(s) in /var/db/pkg");

  script_set_attribute(
    attribute:"synopsis", 
    value:
"The remote Gentoo host is missing one or more security-related
patches."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"The remote host is affected by the vulnerability described in GLSA-201702-23
(Dropbear: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in Dropbear. Please review
      the CVE identifiers referenced below for details.
  
Impact :

    A remote attacker could possibly execute arbitrary code with root
      privileges if usernames containing special characters can be created on a
      system. Also, a dbclient user who can control username or host arguments
      could potentially run arbitrary code with the privileges of the process.
    In addition, a remote attacker could entice a user to process a
      specially crafted SSH key using dropbearconvert, possibly resulting in
      execution of arbitrary code with the privileges of the process or a
      Denial of Service condition.
  
Workaround :

    There is no known workaround at this time."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://security.gentoo.org/glsa/201702-23"
  );
  script_set_attribute(
    attribute:"solution", 
    value:
"All Dropbear users should upgrade to the latest version:
      # emerge --sync
      # emerge --ask --oneshot --verbose '>=net-misc/dropbear-2016.74'"
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A: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_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:gentoo:linux:dropbear");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:gentoo:linux");

  script_set_attribute(attribute:"patch_publication_date", value:"2017/02/20");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/02/21");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2017 Tenable Network Security, Inc.");
  script_family(english:"Gentoo Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Gentoo/release", "Host/Gentoo/qpkg-list");

  exit(0);
}


include("audit.inc");
include("global_settings.inc");
include("qpkg.inc");

if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/Gentoo/release")) audit(AUDIT_OS_NOT, "Gentoo");
if (!get_kb_item("Host/Gentoo/qpkg-list")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;

if (qpkg_check(package:"net-misc/dropbear", unaffected:make_list("ge 2016.74"), vulnerable:make_list("lt 2016.74"))) flag++;

if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:qpkg_report_get());
  else security_hole(0);
  exit(0);
}
else
{
  tested = qpkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "Dropbear");
}

#%NASL_MIN_LEVEL 80502
#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Debian Security Advisory DLA-634-1. The text
# itself is copyright (C) Software in the Public Interest, Inc.
#

include("compat.inc");

if (description)
{
  script_id(93688);
  script_version("2.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/03/12");

  script_name(english:"Debian DLA-634-1 : dropbear security update");
  script_summary(english:"Checks dpkg output for the updated package.");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Debian host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"It was discovered that there were two issues in dropbear, a
lightweight SSH2 server and client :

  - CVE-2016-7406: Potential issues in exit message
    formatting.

  - CVE-2016-7407: Overflows when parsing OpenSSH's ASN.1
    key format.

For Debian 7 'Wheezy', this issue has been fixed in dropbear version
2012.55-1.3+deb7u1.

We recommend that you upgrade your dropbear packages.

NOTE: Tenable Network Security has extracted the preceding description
block directly from the DLA security advisory. Tenable has attempted
to automatically clean and format it as much as possible without
introducing additional issues."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://lists.debian.org/debian-lts-announce/2016/09/msg00027.html"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://packages.debian.org/source/wheezy/dropbear"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Upgrade the affected dropbear package."
  );
  script_set_attribute(attribute:"risk_factor", value:"High");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:dropbear");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:7.0");

  script_set_attribute(attribute:"patch_publication_date", value:"2016/09/23");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/09/26");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2016-2020 Tenable Network Security, Inc.");
  script_family(english:"Debian Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Debian/release", "Host/Debian/dpkg-l");

  exit(0);
}


include("audit.inc");
include("debian_package.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/Debian/release")) audit(AUDIT_OS_NOT, "Debian");
if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;
if (deb_check(release:"7.0", prefix:"dropbear", reference:"2012.55-1.3+deb7u1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:deb_report_get());
  else security_hole(0);
  exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");