FreeBSD : OpenSSH -- Double-free memory corruption in ssh-agent (76b5068c-8436-11eb-9469-080027f515ea)

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from the FreeBSD VuXML database :
#
# Copyright 2003-2021 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(147897);
  script_version("1.6");
  script_set_attribute(attribute:"plugin_modification_date", value:"2021/10/18");

  script_cve_id("CVE-2021-28041");
  script_xref(name:"IAVA", value:"2021-A-0121-S");

  script_name(english:"FreeBSD : OpenSSH -- Double-free memory corruption in ssh-agent (76b5068c-8436-11eb-9469-080027f515ea)");
  script_summary(english:"Checks for updated packages in pkg_info output");

  script_set_attribute(
    attribute:"synopsis",
    value:
"The remote FreeBSD host is missing one or more security-related
updates."
  );
  script_set_attribute(
    attribute:"description",
    value:
"OpenBSD Project reports :

ssh-agent(1): fixed a double-free memory corruption that was
introduced in OpenSSH 8.2 . We treat all such memory faults as
potentially exploitable. This bug could be reached by an attacker with
access to the agent socket.

On modern operating systems where the OS can provide information about
the user identity connected to a socket, OpenSSH ssh-agent and sshd
limit agent socket access only to the originating user and root.
Additional mitigation may be afforded by the system's
malloc(3)/free(3) implementation, if it detects double-free
conditions.

The most likely scenario for exploitation is a user forwarding an
agent either to an account shared with a malicious user or to a host
with an attacker holding root access."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://www.openssh.com/txt/release-8.5"
  );
  # https://vuxml.freebsd.org/freebsd/76b5068c-8436-11eb-9469-080027f515ea.html
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.nessus.org/u?8d0bca2f"
  );
  script_set_attribute(attribute:"solution", value:"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:H/Au:S/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:H/PR:L/UI:R/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-2021-28041");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:freebsd:freebsd:openssh-portable");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:freebsd:freebsd:openssh-portable-gssapi");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:freebsd:freebsd:openssh-portable-hpn");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:freebsd:freebsd");

  script_set_attribute(attribute:"vuln_publication_date", value:"2021/03/03");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/03/13");
  script_set_attribute(attribute:"plugin_publication_date", value:"2021/03/19");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_set_attribute(attribute:"stig_severity", value:"I");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2021 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:"openssh-portable>=8.2.p1,1<8.4.p1_4,1")) flag++;
if (pkg_test(save_report:TRUE, pkg:"openssh-portable-hpn>=8.2.p1,1<8.4.p1_4,1")) flag++;
if (pkg_test(save_report:TRUE, pkg:"openssh-portable-gssapi>=8.2.p1,1<8.4.p1_4,1")) flag++;

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