Vulnerabilities > CVE-2017-3857 - Resource Exhaustion vulnerability in Cisco IOS

047910
CVSS 7.5 - HIGH
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
NONE
Availability impact
HIGH
network
low complexity
cisco
CWE-400
nessus
NVD
Published: 2017-03-22
Updated: 2024-11-21

Summary

A vulnerability in the Layer 2 Tunneling Protocol (L2TP) parsing function of Cisco IOS (12.0 through 12.4 and 15.0 through 15.6) and Cisco IOS XE (3.1 through 3.18) could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to insufficient validation of L2TP packets. An attacker could exploit this vulnerability by sending a crafted L2TP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or Cisco IOS XE Software if the L2TP feature is enabled for the device and the device is configured as an L2TP Version 2 (L2TPv2) or L2TP Version 3 (L2TPv3) endpoint. By default, the L2TP feature is not enabled. Cisco Bug IDs: CSCuy82078.

Vulnerable Configurations

Part Description Count
OS
Cisco
5537

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • XML Ping of the Death
    An attacker initiates a resource depletion attack where a large number of small XML messages are delivered at a sufficiently rapid rate to cause a denial of service or crash of the target. Transactions such as repetitive SOAP transactions can deplete resources faster than a simple flooding attack because of the additional resources used by the SOAP protocol and the resources necessary to process SOAP messages. The transactions used are immaterial as long as they cause resource utilization on the target. In other words, this is a normal flooding attack augmented by using messages that will require extra processing on the target.
  • XML Entity Expansion
    An attacker submits an XML document to a target application where the XML document uses nested entity expansion to produce an excessively large output XML. XML allows the definition of macro-like structures that can be used to simplify the creation of complex structures. However, this capability can be abused to create excessive demands on a processor's CPU and memory. A small number of nested expansions can result in an exponential growth in demands on memory.
  • Inducing Account Lockout
    An attacker leverages the security functionality of the system aimed at thwarting potential attacks to launch a denial of service attack against a legitimate system user. Many systems, for instance, implement a password throttling mechanism that locks an account after a certain number of incorrect log in attempts. An attacker can leverage this throttling mechanism to lock a legitimate user out of their own account. The weakness that is being leveraged by an attacker is the very security feature that has been put in place to counteract attacks.
  • Violating Implicit Assumptions Regarding XML Content (aka XML Denial of Service (XDoS))
    XML Denial of Service (XDoS) can be applied to any technology that utilizes XML data. This is, of course, most distributed systems technology including Java, .Net, databases, and so on. XDoS is most closely associated with web services, SOAP, and Rest, because remote service requesters can post malicious XML payloads to the service provider designed to exhaust the service provider's memory, CPU, and/or disk space. The main weakness in XDoS is that the service provider generally must inspect, parse, and validate the XML messages to determine routing, workflow, security considerations, and so on. It is exactly these inspection, parsing, and validation routines that XDoS targets. There are three primary attack vectors that XDoS can navigate Target CPU through recursion: attacker creates a recursive payload and sends to service provider Target memory through jumbo payloads: service provider uses DOM to parse XML. DOM creates in memory representation of XML document, but when document is very large (for example, north of 1 Gb) service provider host may exhaust memory trying to build memory objects. XML Ping of death: attack service provider with numerous small files that clog the system. All of the above attacks exploit the loosely coupled nature of web services, where the service provider has little to no control over the service requester and any messages the service requester sends.

Nessus

  • NASL familyCISCO
    NASL idCISCO-SA-20170322-L2TP-IOSXE.NASL
    descriptionAccording to its self-reported version, the Cisco IOS XE software running on the remote device is affected by a denial of service vulnerability in its Layer 2 Tunneling Protocol (L2TP) parsing function due to insufficient validation of L2TP packets. An unauthenticated, remote attacker can exploit this issue, via a specially crafted L2TP packet, to cause the device to reload. Note that this issue only affects devices if the L2TP feature is enabled and the device is configured as an L2TP Version 2 (L2TPv2) or L2TP Version 3 (L2TPv3) endpoint. By default, the L2TP feature is not enabled.
    last seen2020-06-01
    modified2020-06-02
    plugin id99029
    published2017-03-28
    reporterThis script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/99029
    titleCisco IOS XE L2TP Parsing DoS (cisco-sa-20170322-l2tp)
    code
    #TRUSTED 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
#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(99029);
  script_version("1.8");
  script_cvs_date("Date: 2019/11/13");

  script_cve_id("CVE-2017-3857");
  script_bugtraq_id(97010);
  script_xref(name:"CISCO-BUG-ID", value:"CSCuy82078");
  script_xref(name:"CISCO-SA", value:"cisco-sa-20170322-l2tp");

  script_name(english:"Cisco IOS XE L2TP Parsing DoS (cisco-sa-20170322-l2tp)");
  script_summary(english:"Checks the IOS XE version.");

  script_set_attribute(attribute:"synopsis", value:
"The remote device is missing a vendor-supplied security patch.");
  script_set_attribute(attribute:"description", value:
"According to its self-reported version, the Cisco IOS XE software
running on the remote device is affected by a denial of service
vulnerability in its Layer 2 Tunneling Protocol (L2TP) parsing
function due to insufficient validation of L2TP packets. An
unauthenticated, remote attacker can exploit this issue, via a
specially crafted L2TP packet, to cause the device to reload.

Note that this issue only affects devices if the L2TP feature is
enabled and the device is configured as an L2TP Version 2 (L2TPv2) or
L2TP Version 3 (L2TPv3) endpoint. By default, the L2TP feature is not
enabled.");
  # https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170322-l2tp
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?d4fc7ea8");
  script_set_attribute(attribute:"see_also", value:"https://bst.cloudapps.cisco.com/bugsearch/bug/CSCuy82078");
  script_set_attribute(attribute:"solution", value:
"Upgrade to the relevant fixed version referenced in Cisco bug ID
CSCuy82078.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:N/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:N/I:N/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-2017-3857");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/03/22");
  script_set_attribute(attribute:"patch_publication_date", value:"2017/03/22");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/03/28");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:cisco:ios_xe");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("cisco_ios_xe_version.nasl");
  script_require_keys("Host/Cisco/IOS-XE/Version");

  exit(0);
}

include("audit.inc");
include("cisco_workarounds.inc");
include("ccf.inc");

product_info = cisco::get_product_info(name:"Cisco IOS XE Software");

version_list = make_list(
  "3.4.0S",
  "3.4.1S",
  "3.4.2S",
  "3.4.3S",
  "3.4.4S",
  "3.4.5S",
  "3.4.6S",
  "3.4.0aS",
  "3.4.7S",
  "3.5.0S",
  "3.5.1S",
  "3.5.2S",
  "3.5.0aS",
  "3.6.0S",
  "3.6.1S",
  "3.6.2S",
  "3.7.0S",
  "3.7.1S",
  "3.7.2S",
  "3.7.3S",
  "3.7.4S",
  "3.7.5S",
  "3.7.6S",
  "3.7.7S",
  "3.7.8S",
  "3.7.4aS",
  "3.7.2tS",
  "3.7.0bS",
  "3.7.1aS",
  "3.8.0S",
  "3.8.1S",
  "3.8.2S",
  "3.9.1S",
  "3.9.0S",
  "3.9.2S",
  "3.9.1aS",
  "3.9.0aS",
  "3.3.0XO",
  "3.3.1XO",
  "3.3.2XO",
  "3.10.0S",
  "3.10.1S",
  "3.10.2S",
  "3.10.3S",
  "3.10.4S",
  "3.10.5S",
  "3.10.6S",
  "3.10.1xcS",
  "3.10.2aS",
  "3.10.2tS",
  "3.10.7S",
  "3.10.1xbS",
  "3.10.8S",
  "3.10.8aS",
  "3.11.1S",
  "3.11.2S",
  "3.11.0S",
  "3.11.3S",
  "3.11.4S",
  "3.12.0S",
  "3.12.1S",
  "3.12.2S",
  "3.12.3S",
  "3.12.0aS",
  "3.12.4S",
  "3.13.0S",
  "3.13.1S",
  "3.13.2S",
  "3.13.3S",
  "3.13.4S",
  "3.13.5S",
  "3.13.2aS",
  "3.13.0aS",
  "3.13.5aS",
  "3.6.0aE",
  "3.6.2aE",
  "3.6.5bE",
  "3.14.0S",
  "3.14.1S",
  "3.14.2S",
  "3.14.3S",
  "3.14.4S",
  "3.15.0S",
  "3.15.1S",
  "3.15.2S",
  "3.15.1xbS",
  "3.15.1cS",
  "3.15.2xbS",
  "3.15.3S",
  "3.15.4S",
  "3.3.0SQ",
  "3.3.1SQ",
  "3.4.0SQ",
  "3.4.1SQ",
  "3.7.4E",
  "3.5.0SQ",
  "3.5.1SQ",
  "3.5.2SQ",
  "3.5.3SQ",
  "3.5.4SQ",
  "3.16.0S",
  "3.16.1S",
  "3.16.0aS",
  "3.16.1aS",
  "3.16.2S",
  "3.16.2aS",
  "3.16.0bS",
  "3.16.0cS",
  "3.16.2bS",
  "3.17.0S",
  "3.17.1S",
  "3.17.1aS",
  "16.2.1",
  "3.18.0aS",
  "3.18.0S",
  "3.18.4S"
);

workarounds = make_list(CISCO_WORKAROUNDS['L2TP_check']);
workaround_params = make_list();

reporting = make_array(
  'port'     , 0,
  'severity' , SECURITY_HOLE,
  'version'  , product_info['version'],
  'bug_id'   , "CSCuy82078",
  'cmds'     , make_list("show running-config")
);

cisco::check_and_report(product_info:product_info, workarounds:workarounds, workaround_params:workaround_params, reporting:reporting, vuln_versions:version_list);
  • NASL familyCISCO
    NASL idCISCO-SA-20170322-L2TP-IOS.NASL
    descriptionAccording to its self-reported version, the Cisco IOS software running on the remote device is affected by a denial of service vulnerability in its Layer 2 Tunneling Protocol (L2TP) parsing function due to insufficient validation of L2TP packets. An unauthenticated, remote attacker can exploit this issue, via a specially crafted L2TP packet, to cause the device to reload. Note that this issue only affects devices if the L2TP feature is enabled and the device is configured as an L2TP Version 2 (L2TPv2) or L2TP Version 3 (L2TPv3) endpoint. By default, the L2TP feature is not enabled.
    last seen2020-06-01
    modified2020-06-02
    plugin id99028
    published2017-03-28
    reporterThis script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/99028
    titleCisco IOS L2TP Parsing DoS (cisco-sa-20170322-l2tp)

References