Vulnerabilities > CVE-2018-0334 - Improper Certificate Validation vulnerability in Cisco Anyconnect Secure Mobility Client 4.6(100)

047910
CVSS 4.8 - MEDIUM
Attack vector
NETWORK
Attack complexity
HIGH
Privileges required
NONE
Confidentiality impact
LOW
Integrity impact
LOW
Availability impact
NONE
network
high complexity
cisco
CWE-295
nessus
NVD
Published: 2018-06-07
Updated: 2024-11-21

Summary

A vulnerability in the certificate management subsystem of Cisco AnyConnect Network Access Manager and of Cisco AnyConnect Secure Mobility Client for iOS, Mac OS X, Android, Windows, and Linux could allow an unauthenticated, remote attacker to bypass the TLS certificate check when downloading certain configuration files. The vulnerability is due to improper use of Simple Certificate Enrollment Protocol and improper server certificate validation. An attacker could exploit this vulnerability by preparing malicious profile and localization files for Cisco AnyConnect to use. A successful exploit could allow the attacker to remotely change the configuration profile, a certificate, or the localization data used by AnyConnect Secure Mobility Client. Cisco Bug IDs: CSCvh23141.

Vulnerable Configurations

Part Description Count
Application
Cisco
1

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Creating a Rogue Certificate Authority Certificate
    An attacker exploits a weakness in the MD5 hash algorithm (weak collision resistance) to generate a certificate signing request (CSR) that contains collision blocks in the "to be signed" part. The attacker specially crafts two different, but valid X.509 certificates that when hashed with the MD5 algorithm would yield the same value. The attacker then sends the CSR for one of the certificates to the Certification Authority which uses the MD5 hashing algorithm. That request is completely valid and the Certificate Authority issues an X.509 certificate to the attacker which is signed with its private key. An attacker then takes that signed blob and inserts it into another X.509 certificate that the attacker generated. Due to the MD5 collision, both certificates, though different, hash to the same value and so the signed blob works just as well in the second certificate. The net effect is that the attackers' second X.509 certificate, which the Certification Authority has never seen, is now signed and validated by that Certification Authority. To make the attack more interesting, the second certificate could be not just a regular certificate, but rather itself a signing certificate. Thus the attacker is able to start their own Certification Authority that is anchored in its root of trust in the legitimate Certification Authority that has signed the attackers' first X.509 certificate. If the original Certificate Authority was accepted by default by browsers, so will now the Certificate Authority set up by the attacker and of course any certificates that it signs. So the attacker is now able to generate any SSL certificates to impersonate any web server, and the user's browser will not issue any warning to the victim. This can be used to compromise HTTPS communications and other types of systems where PKI and X.509 certificates may be used (e.g., VPN, IPSec) .

Nessus

NASL familyWindows
NASL idCISCO_ANYCONNECT_CSCVH23141.NASL
descriptionThe version of Cisco AnyConnect Secure Mobility Client installed on the remote Windows host is prior to 4.6.01098. It is, therefore, affected by a certificate bypass vulnerability.
last seen2020-06-01
modified2020-06-02
plugin id110563
published2018-06-15
reporterThis script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
sourcehttps://www.tenable.com/plugins/nessus/110563
titleCisco AnyConnect Secure Mobility Client < 4.6.01098 Certificate Bypass Vulnerability
code
#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(110563);
  script_version("1.5");
  script_cvs_date("Date: 2019/11/04");

  script_cve_id("CVE-2018-0334");
  script_bugtraq_id(104430);
  script_xref(name:"CISCO-SA", value:"cisco-sa-20180606-AnyConnect-cert-bypass");
  script_xref(name:"CISCO-BUG-ID", value:"CSCvh23141");

  script_name(english:"Cisco AnyConnect Secure Mobility Client < 4.6.01098 Certificate Bypass Vulnerability");
  script_summary(english:"Checks the version of the Cisco AnyConnect client.");

  script_set_attribute(attribute:"synopsis", value:
"A VPN application installed on the remote host is affected by a
certificate bypass vulnerability.");
  script_set_attribute(attribute:"description", value:
"The version of Cisco AnyConnect Secure Mobility Client installed on
the remote Windows host is prior to 4.6.01098. It is, therefore,
affected by a certificate bypass vulnerability.");
  # https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180606-AnyConnect-cert-bypass
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?327a2cae");
  script_set_attribute(attribute:"solution", value:
"Upgrade to Cisco AnyConnect Secure Mobility Client version 4.6.01098 
or later.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:P/I:P/A:N");
  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:N/UI:N/S:U/C:L/I:L/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2018-0334");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/06/06");
  script_set_attribute(attribute:"patch_publication_date", value:"2017/06/06");
  script_set_attribute(attribute:"plugin_publication_date", value:"2018/06/15");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:cisco:anyconnect_secure_mobility_client");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Windows");

  script_copyright(english:"This script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("cisco_anyconnect_vpn_installed.nasl");
  script_require_keys("installed_sw/Cisco AnyConnect Secure Mobility Client", "SMB/Registry/Enumerated");
  script_require_ports(139, 445);

  exit(0);
}

include("vcf.inc");

get_kb_item_or_exit("SMB/Registry/Enumerated");
app_info = vcf::get_app_info(app:"Cisco AnyConnect Secure Mobility Client", win_local:TRUE);

constraints = [
  { "fixed_version":"4.5.05030" },
  { "min_version":"4.6", "fixed_version":"4.6.01098" }
];

vcf::check_version_and_report(app_info:app_info, constraints:constraints, severity:SECURITY_WARNING);

References