Vulnerabilities > CVE-2016-5302 - Improper Access Control vulnerability in Citrix Xenserver

047910
CVSS 7.5 - HIGH
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
PARTIAL
Integrity impact
PARTIAL
Availability impact
PARTIAL
network
low complexity
citrix
CWE-284
nessus

Summary

Citrix XenServer 7.0 before Hotfix XS70E003, when a deployment has been upgraded from an earlier release, might allow remote attackers on the management network to "compromise" a host by leveraging credentials for an Active Directory account.

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Embedding Scripts within Scripts
    An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute scripts. The attacker leverages this capability to execute scripts to execute his/her own script by embedding it within other scripts that the target software is likely to execute. The attacker must have the ability to inject script into script that is likely to be executed. If this is done, then the attacker can potentially launch a variety of probes and attacks against the web server's local environment, in many cases the so-called DMZ, back end resources the web server can communicate with, and other hosts. With the proliferation of intermediaries, such as Web App Firewalls, network devices, and even printers having JVMs and Web servers, there are many locales where an attacker can inject malicious scripts. Since this attack pattern defines scripts within scripts, there are likely privileges to execute said attack on the host. Of course, these attacks are not solely limited to the server side, client side scripts like Ajax and client side JavaScript can contain malicious scripts as well. In general all that is required is for there to be sufficient privileges to execute a script, but not protected against writing.
  • Signature Spoofing by Key Theft
    An attacker obtains an authoritative or reputable signer's private signature key by theft and then uses this key to forge signatures from the original signer to mislead a victim into performing actions that benefit the attacker.

Nessus

NASL familyMisc.
NASL idCITRIX_XENSERVER_CTX213549.NASL
descriptionThe version of Citrix XenServer running on the remote host is 7.x prior to 7.0 hotfix XS70E003. It is, therefore, affected by a security bypass vulnerability due to incorrect handling of Active Directory (AD) credentials. An unauthenticated, remote attacker on the management network with AD credentials for an AD account can exploit this to compromise the XenServer host even if the credentials do not have authorization.
last seen2020-06-01
modified2020-06-02
plugin id91885
published2016-06-28
reporterThis script is Copyright (C) 2016-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
sourcehttps://www.tenable.com/plugins/nessus/91885
titleCitrix XenServer Active Directory Authentication Incorrect Host Management Security Bypass (CTX213549, CTX213769)
code
#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(91885);
  script_version("1.5");
  script_cvs_date("Date: 2019/11/14");

  script_cve_id("CVE-2016-5302");

  script_name(english:"Citrix XenServer Active Directory Authentication Incorrect Host Management Security Bypass (CTX213549, CTX213769)");
  script_summary(english:"Checks for patches.");

  script_set_attribute(attribute:"synopsis", value:
"The remote host is affected by a security bypass vulnerability.");
  script_set_attribute(attribute:"description", value:
"The version of Citrix XenServer running on the remote host is 7.x
prior to 7.0 hotfix XS70E003. It is, therefore, affected by a security
bypass vulnerability due to incorrect handling of Active Directory
(AD) credentials. An unauthenticated, remote attacker on the
management network with AD credentials for an AD account can exploit
this to compromise the XenServer host even if the credentials do not
have authorization.");
  script_set_attribute(attribute:"see_also", value:"https://support.citrix.com/article/CTX213549");
  script_set_attribute(attribute:"see_also", value:"https://support.citrix.com/article/CTX213769");
  script_set_attribute(attribute:"solution", value:
"Apply hotfix XS70E003 as referenced in the vendor advisory.");
  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:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"vuln_publication_date", value:"2016/06/09");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/06/09");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/06/28");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:citrix:xenserver");
  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("citrix_xenserver_version.nbin");
  script_require_keys("Settings/ParanoidReport", "Host/XenServer/version", "Host/local_checks_enabled");

  exit(0);
}

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

app_name = "Citrix XenServer";
version = get_kb_item_or_exit("Host/XenServer/version");
get_kb_item_or_exit("Host/local_checks_enabled");
patches = get_kb_item("Host/XenServer/patches");

# There are several mitigations for this issue:
#   - If AD auth has even briefly been disabled, the host is not vulnerable.
#   - This is only true for versions that have been upgraded from < 7 to 7.x,
#     not for new 7.0 installs
if (report_paranoia < 2)
  audit(AUDIT_PARANOID);

vuln = FALSE;
fix = 'XS70E003';

if (version !~ "^7\.0\.")
  audit(AUDIT_INST_VER_NOT_VULN, app_name, version);
else if (fix >< patches)
  audit(AUDIT_INST_VER_NOT_VULN, app_name, version + " with hotfix " +fix);
else
{
  port = 0;
  items = make_array("Installed version", version,
                     "Missing hotfix", fix
                    );

  order = make_list("Installed version", "Missing hotfix");
  report = report_items_str(report_items:items, ordered_fields:order);

  security_report_v4(port:port, severity:SECURITY_HOLE, extra:report);
  exit(0);
}