Cisco FXOS and NX-OS Software Cisco Fabric Services Arbitrary Code Execution Vulnerability [CVE-2018-0308]

CVE Number – CVE-2018-0308

  • A vulnerability in the Cisco Fabric Services component of Cisco FXOS Software and Cisco NX-OS Software could allow an unauthenticated, remote attacker to execute arbitrary code or cause a denial of service (DoS) condition.

    The vulnerability exists because the affected software insufficiently validates header values in Cisco Fabric Services packets. An attacker could exploit this vulnerability by sending a crafted Cisco Fabric Services packet to an affected device. A successful exploit could allow the attacker to cause a buffer overflow that could allow the attacker to execute arbitrary code or cause a DoS condition.

    Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

    This advisory is available at the following link:
    https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180620-fxnxos-fab-ace

    This advisory is part of the June 2018 Cisco FXOS and NX-OS Software Security Advisory Collection, which includes 24 Cisco Security Advisories that describe 24 vulnerabilities. For a complete list of the advisories and links to them, see Cisco Event Response: June 2018 Cisco FXOS and NX-OS Software Security Advisory Collection.

Affected Products
  • Vulnerable Products

    This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco FXOS Software or Cisco NX-OS Software and are configured to use Cisco Fabric Services:

    • Firepower 4100 Series Next-Generation Firewalls
    • Firepower 9300 Security Appliance
    • MDS 9000 Series Multilayer Switches
    • Nexus 2000 Series Fabric Extenders
    • Nexus 3000 Series Switches
    • Nexus 3500 Platform Switches
    • Nexus 5500 Platform Switches
    • Nexus 5600 Platform Switches
    • Nexus 6000 Series Switches
    • Nexus 7000 Series Switches
    • Nexus 7700 Series Switches
    • Nexus 9000 Series Switches in standalone NX-OS mode
    • Nexus 9500 R-Series Line Cards and Fabric Modules
    • UCS 6100 Series Fabric Interconnects
    • UCS 6200 Series Fabric Interconnects
    • UCS 6300 Series Fabric Interconnects

    For information about which Cisco FXOS and NX-OS Software releases are vulnerable, see the Fixed Software section of this advisory.

    For information about determining whether a device is configured to use Cisco Fabric Services, see the Details section of this advisory.

    Determining the Cisco FXOS Software Release

    Administrators can check the release of Cisco FXOS Software that is running on a device by using the following commands in the device CLI or by navigating to the Overview tab in the Admin portal. The following example shows the output of the show version CLI command on a device that is running Cisco FXOS Software Release 2.2(2.14), as identified in the Package-Vers field of the command output:

    QP4120B1 # scope system
    QP4120B1 /system # show version
    FPRM:
    Running-Vers: 4.2(2.15)
    Package-Vers: 2.2(2.14)
    Activate-Status: Ready

    Determining the Cisco NX-OS Software Release

    Administrators can check the release of Cisco NX-OS Software that is running on a device by using the show version command in the device CLI. The following example shows the output of this command on a device that is running Cisco NX-OS Software Release 7.3(2)D1(1):

    nxos-switch# show version
    Cisco Nexus Operating System (NX-OS) Software
    TAC support: http://www.cisco.com/tac
    Documents: http://www.cisco.com/en/US/products/ps9372/tsd_products_support_series_home.html
    Copyright (c) 2002-2017, Cisco Systems, Inc. All rights reserved.
    The copyrights to certain works contained in this software are
    owned by other third parties and used and distributed under
    license. Certain components of this software are licensed under
    the GNU General Public License (GPL) version 2.0 or the GNU
    Lesser General Public License (LGPL) Version 2.1. A copy of each
    such license is available at
    http://www.opensource.org/licenses/gpl-2.0.php and
    http://www.opensource.org/licenses/lgpl-2.1.php
    Software
      BIOS:      version 2.12.0
      kickstart: version 7.3(2)D1(1)
      system:    version 7.3(2)D1(1)
    .
    .
    .
    
    




    Products Confirmed Not Vulnerable

    Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.

    Cisco has confirmed that this vulnerability does not affect the following Cisco products:

    • Firepower 2100 Series Firewalls
    • Nexus 1000V Series Switches
    • Nexus 1100 Series Cloud Services Platforms
    • Nexus 3600 Platform Switches
    • Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode

    Cisco has not investigated whether this vulnerability affects Cisco Nexus 4000 Series Switches, Cisco Nexus 5010 Switches, or Cisco Nexus 5020 Switches because those products have reached end-of-life status. For more information, refer to the End-of-Sale and End-of-Life Announcement for the Cisco Nexus 4000 Series Switch Modules for IBM BladeCenter and the End-of-Sale and End-of-Life Announcement for the Cisco Nexus 5010 and Nexus 5020 Switches.

Details
  • Cisco Fabric Services provides a common infrastructure for distributing and synchronizing configuration data between Cisco devices that are on the same network and with virtual port channels (vPCs). This includes configuration data for applications and features that are compatible with and enabled to use Cisco Fabric Services—for example, Distributed Device Alias Services, Network Time Protocol (NTP), and user and administrator roles.

    To distribute and synchronize data, Cisco Fabric Services can be configured to use any of the following distribution types:

    • Cisco Fabric Services over Fibre Channel (CFSoFC)—Distributes data over a Fibre Channel (FC), such as a virtual storage area network (VSAN). CFSoFC distribution is enabled by default.
    • Cisco Fabric Services over Ethernet (CFSoE)—Distributes data over an Ethernet network. For vPC support, Cisco Fabric Services must be configured to use this distribution type. CFSoE distribution is disabled by default.
    • Cisco Fabric Services over IP (CFSoIP)—Distributes data over an IPv4 or IPv6 network. CFSoIP distribution is disabled by default.

    The vulnerability described in this advisory is due to insufficient input validation that could occur when the affected software processes Cisco Fabric Services packets that it receives during distribution and synchronization operations. Exploitation of the vulnerability does not require any applications to be enabled to use Cisco Fabric Services. Instead, exploitation depends on which Cisco Fabric Services distribution types are configured for a device. In addition, the attack vectors vary based on which distribution types are configured, as follows:

    • CFSoFC—An attack could occur via Fibre Channel over Ethernet (FCoE) or Fibre Channel over IP (FCIP), if FC ports are configured for a device. In this scenario, an attack could succeed in the data plane, not the management plane, of any FC port. If no FC ports are configured for a device, this distribution type cannot be used to exploit the vulnerability.
    • CFSoE—An attack is possible from only a vPC peer or an attacker who has access to a vPC peer link. No other peer, neighbor, or network node can be used to exploit the vulnerability.
    • CFSoIP—An attack is possible from any node that has IP network connectivity to the management interface of a device. In this scenario, an attack cannot succeed from the data plane.

    If a device is enabled to use more than one distribution type, the applicable attack vectors for all those distribution types exist for the device.

    Administrators can display configuration information and check the distribution status of Cisco Fabric Services for a device by using the show cfs status command in the device CLI, as shown in the following example:

    switch# show cfs status
    Distribution : Enabled
    Distribution over IP : Disabled
    IPv4 multicast address : 239.255.70.83
    IPv6 multicast address : ff15::efff:4653
    Distribution over Ethernet : Disabled

    In the preceding example, the Enabled value in the Distribution field of the command output indicates that Cisco Fabric Services is enabled for the device and the device is configured to use the default Cisco Fabric Services distribution type, which is CFSoFC. The Disabled value in the Distribution over IP field and the Distribution over Ethernet field indicates that the device is not additionally configured to use the CFSoIP and CFSoE distribution types.

Workarounds
  • There are no workarounds that address this vulnerability.

Fixed Software
  • Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
    https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

    Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.

    When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.

    In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

    Customers Without Service Contracts

    Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco TAC:
    https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

    Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.

    Fixed Releases

    Customers are advised to upgrade to an appropriate release as indicated in the applicable table in this section. To help ensure a complete upgrade solution, consider that this advisory is part of a collection. For a complete list of the advisories in the collection and links to them, see Cisco Event Response: June 2018 Cisco FXOS and NX-OS Software Security Advisory Collection.

    In the following tables, the left column lists releases of Cisco FXOS or NX-OS Software. The center column indicates whether a release is affected by the vulnerability described in this advisory and the first release that includes the fix for this vulnerability. The right column indicates whether a release is affected by all the vulnerabilities described in this collection of advisories and which release includes fixes for those vulnerabilities.

    Firepower 4100 Series Next-Generation Firewalls: CSCve04859

    Cisco FXOS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    1.1 1.1.4.179 2.2.2.17 or 2.3.1.58
    2.0 2.0.1.153 2.2.2.17 or 2.3.1.58
    2.1.1 2.1.1.86 2.2.2.17 or 2.3.1.58
    2.2.1 2.2.1.70 2.2.2.17 or 2.3.1.58
    2.2.2 2.2.2.17 2.2.2.17 or 2.3.1.58
    2.3 Not vulnerable Not vulnerable

    Firepower 9300 Security Appliance: CSCve04859

    Cisco FXOS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    1.1 1.1.4.179 2.2.2.17 or 2.3.1.58
    2.0 2.0.1.153 2.2.2.17 or 2.3.1.58
    2.1.1 2.1.1.86 2.2.2.17 or 2.3.1.58
    2.2.1 2.2.1.70 2.2.2.17 or 2.3.1.58
    2.2.2 2.2.2.17 2.2.2.17 or 2.3.1.58
    2.3 Not vulnerable Not vulnerable

    MDS 9000 Series Multilayer Switches: CSCvd69954

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    5.2 6.2(21) 8.1(2) or 8.2(1)
    6.2 6.2(21) 8.1(2) or 8.2(1)
    7.3 8.1(1a) 8.1(2) or 8.2(1)
    8.1 8.1(1a) 8.1(2) or 8.2(1)
    8.2 Not vulnerable Not vulnerable

    Nexus 3000 Series Switches: CSCve02785

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    Prior to 7.0(3)I4 7.0(3)I4(7) 7.0(3)I7(4)
    7.0(3)I4 7.0(3)I4(7) 7.0(3)I7(4)
    7.0(3)I5 7.0(3)I6(2) 7.0(3)I7(4)
    7.0(3)I6 7.0(3)I6(2) 7.0(3)I7(4)
    7.0(3)I7 Not vulnerable 7.0(3)I7(4)

    Nexus 3500 Platform Switches: CSCve02785

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    6.0 7.0(3)I7(2) 7.0(3)I7(4)
    7.0.3 Not vulnerable 7.0(3)I7(4)

    Nexus 2000, 5500, 5600, and 6000 Series Switches: CSCve02463

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    6.0 7.3(3)N1(1) 7.3(3)N1(1)
    7.0 7.3(3)N1(1) 7.3(3)N1(1)
    7.1 7.3(3)N1(1) 7.3(3)N1(1)
    7.2 7.3(3)N1(1) 7.3(3)N1(1)
    7.3 7.3(3)N1(1) 7.3(3)N1(1)

    Nexus 7000 and 7700 Series Switches: CSCvd69954

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    6.2 6.2(20) 8.1(2) or 8.2(1)
    7.2 7.3(2)D1(1) 8.1(2) or 8.2(1)
    7.3 7.3(2)D1(1) 8.1(2) or 8.2(1)
    8.0 8.1(2) 8.1(2) or 8.2(1)
    8.1 8.1(2) 8.1(2) or 8.2(1)
    8.2 Not vulnerable Not vulnerable

    Nexus 9000 Series Switches in standalone NX-OS mode: CSCve02785

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    Prior to 7.0(3)I4 7.0(3)I4(7) 7.0(3)I7(4)
    7.0(3)I4 7.0(3)I4(7) 7.0(3)I7(4)
    7.0(3)I5 7.0(3)I6(2) 7.0(3)I7(4)
    7.0(3)I6 7.0(3)I6(2) 7.0(3)I7(4)
    7.0(3)I7 Not vulnerable 7.0(3)I7(4)

    Nexus 9500 R-Series Line Cards and Fabric Modules: CSCve02804

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    7.0 7.0(3)F3(1) 7.0(3)F3(3a)

    UCS 6100, 6200, and 6300 Fabric Interconnects: CSCve02787

    Cisco NX-OS Software Release First Fixed Release for This Vulnerability First Fixed Release for All Vulnerabilities Described in the Collection of Advisories
    Prior to 2.2 3.2(2b) 3.2(2b)
    2.2 3.2(2b) 3.2(2b)
    2.5 3.2(2b) 3.2(2b)
    3.0 3.2(2b) 3.2(2b)
    3.1 3.2(2b) 3.2(2b)
    3.2 3.2(2b) 3.2(2b)
Exploitation and Public Announcements
  • The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.




Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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