Cisco NX-OS Software SNMP Packet Denial of Service Vulnerability

Summary

• A vulnerability in the Simple Network Management Protocol (SNMP) input packet processor of Cisco Nexus 5500 Platform Switches, Cisco Nexus 5600 Platform Switches, and Cisco Nexus 6000 Series Switches running Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause the SNMP application on an affected device to restart unexpectedly.
  
  The vulnerability is due to improper validation of SNMP Protocol Data Units (PDUs) in SNMP packets. An attacker could exploit this vulnerability by sending a crafted SNMP packet to an affected device, which could cause the SNMP application on the device to restart. A successful exploit could allow the attacker to cause the SNMP application to restart multiple times, leading to a system-level restart and a denial of service (DoS) condition.
  
  Cisco released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
  
  This advisory is available at the following link:
  
  http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160302-n5ksnmp

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Nexus 5500 Platform Switches, Cisco Nexus 5600 Platform Switches, and Cisco Nexus 6000 Series Switches running Cisco NX-OS Software Release 7.1(1)N1(1).
  
  To determine whether a device is running a vulnerable release of Cisco NX-OS Software, administrators can use the show version command in the NX-OS command-line interface. The following example shows the output of this command for a Cisco Nexus 5500 Platform Switch running Cisco NX-OS Software Release 7.1(1)N1(1):
  

  # 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) 2002-2012, Cisco Systems, Inc. All rights reserved.
  The copyrights to certain works contained herein are owned by
  other third parties and are used and distributed under license.
  Some parts of this software are covered under the GNU Public
  License. A copy of the license is available at
  http://www.gnu.org/licenses/gpl.html.
  
  Software
  BIOS:      version 3.6.0
  loader:    version N/A
  kickstart: version 7.1(1)N1(1)
  system:    version 7.1(1)N1(1)
  .
  .
  .
  

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by this vulnerability.
  
  Cisco has confirmed that this vulnerability does not affect the following Cisco products:
  

  • Cisco Multilayer Director Switches
  • Cisco Nexus 1000 Series Switches
  • Cisco Nexus 2000 Series Switches
  • Cisco Nexus 3000 Series Switches
  • Cisco Nexus 3500 Series Switches
  • Cisco Nexus 4000 Series Switches
  • Cisco Nexus 5000 Series Switches, except Cisco Nexus 5500 and Cisco Nexus 5600 Platform Switches
  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7700 Series Switches
  • Cisco Nexus 9000 Series Switches
  • Cisco Unified Computing System (UCS) 6100 Series Fabric Interconnects
  • Cisco Unified Computing System (UCS) 6200 Series Fabric Interconnects

Indicators of Compromise

• Exploitation of this vulnerability could cause an affected device to reload and generate an SNMP core file. To view the SNMP core file, administrators can use the show core command in the NX-OS CLI. Contact the Cisco Technical Assistance Center (TAC) to review the SNMP core file and determine whether the device has been compromised by exploitation of this vulnerability.

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: http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.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 consult the Cisco Security Advisories and Responses archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.
  
  In all cases, customers should ensure that the devices to upgrade 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 Technical Assistance Center (TAC): http://www.cisco.com/en/US/support/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 should 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 that includes the following advisories:

  • cisco-sa-20160302-n5ksnmp: Cisco NX-OS Software SNMP Packet Denial of Service Vulnerability
  • cisco-sa-20160302-netstack: Cisco NX-OS Software TCP Netstack Denial of Service Vulnerability
  • cisco-sa-20160302-n3k: Cisco Nexus 3000 Series and 3500 Platform Switches Insecure Default Credentials Vulnerability

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

  Customers should upgrade to an appropriate release as indicated in the following table:

  Cisco NX-OS Software Major Release - Nexus 5500, 5600, and 6000 Series Switches	First Fixed Release for This Vulnerability	First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
  Prior to 5.2	Not affected	7.1(2)N1(1)
  5.2	Not affected	7.1(2)N1(1)
  6.0	Not affected	7.1(2)N1(1)
  7.0	Not affected	7.1(2)N1(1)
  7.1	7.1(2)N1(1)	7.1(2)N1(1)
  7.2	Not affected	7.1(2)N1(1)

  
  Release Recommendations
  
  For additional assistance in determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, refer to the recommended release document for the switch: Cisco Nexus 5500 Platform Switches, Cisco Nexus 5600 Platform Switches, and Cisco Nexus 6000 Series Switches

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.

URL

• http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160302-n5ksnmp

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2016-March-02

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