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Cisco Security Advisory

Cisco NX-OS Malformed IP Packet Denial of Service Vulnerability

Advisory ID: cisco-sa-20120215-nxos

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120215-nxos

Revision 2.0

Last Updated  2012 March 26 21:02  UTC (GMT)

For Public Release 2012 February 15 16:00  UTC (GMT)


Summary

Cisco NX-OS Software is affected by a denial of service (DoS) vulnerability that could cause Cisco Nexus 1000v, 1010, 5000, and 7000 Series Switches, and the Cisco Virtual Security Gateway (VSG) for Nexus 1000V Series Switches, that are running affected versions of Cisco NX-OS Software to reload when the IP stack processes a malformed IP packet.

Cisco has released free software updates that address this vulnerability.

This advisory is available at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120215-nxos

Affected Products


Vulnerable Products

Cisco Nexus 1000v, 1010, 5000, and 7000 Series Switches, and the Cisco VSG for Nexus 1000V Series Switches that are running affected versions of Cisco NX-OS Software are affected by this vulnerability. The vulnerability is in the operating system's IP stack; therefore, any feature that makes use of the services that are offered by the IP stack to process IP packets is affected.

Cisco NX-OS Software versions prior to the First Fixed Release version are affected. Refer to the Software Versions and Fixes section for details regarding fixed versions.

To determine the version of Cisco NX-OS Software that is running on a Cisco Nexus switch, administrators can log in to the device and issue the show version command to display the system banner. The following example shows how to display the version information for the kickstart and system image that is running on a device that runs Cisco NX-OS Release 5.1(3):

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_serie
s_home.html
Copyright (c) 2002-2011, 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 3.22.0
  kickstart: version 5.1(3)
  system:    version 5.1(3)

[...]

Products Confirmed Not Vulnerable

Cisco NX-OS Software for products other than the Cisco Nexus 1000v, 1010, 5000, and 7000 Series Switches, and the Cisco VSG for Nexus 1000V Series Switches, is not affected by this vulnerability. In particular, the following products that run Cisco NX-OS Software are not affected:
  • Cisco Nexus 2000 Series Switches
  • Cisco Nexus 3000 Series Switches
  • Cisco Nexus 4000 Series Switches
  • Unified Computing System (UCS)
  • Cisco MDS 9000 Series Multilayer Switches

No other Cisco products are currently known to be affected by this vulnerability.

Details

Cisco NX-OS Software is the network operating system used by Cisco products that are part of the Cisco Data Center switching portfolio, which includes data center switches such as the Cisco Nexus 5000 Series and the Cisco Nexus 7000 Series.

Certain versions of Cisco NX-OS Software for Cisco Nexus 1000v, 1010, 5000, and 7000 Series Switches, and the Cisco Virtual Security Gateway (VSG) for Nexus 1000V Series Switches, are affected by a vulnerability that may cause a reload of an affected device when the operating system's IP stack processes a malformed IP packet and obtaining Layer 4 (UDP or TCP) information from the packet is required.

The vulnerability is in the operating system's IP stack and any feature that makes use of services offered by the IP stack to parse IP packets is affected. For instance, the following scenarios may trigger the vulnerability because they imply that Layer 4 (UDP or TCP) information is required to be able to perform the configured function:

  • A malformed, transit IP packet that would normally be forwarded by the switch is received and the Time-to-live (TTL) is 1. In this case, an ICMP error message (time exceeded) needs to be generated. During generation of this ICMP message, the bug could be triggered.
  • Policy-based routing is in use, and to make a routing decision, an incoming packet needs to be parsed. If the packet is a malformed TCP segment and the routing policy uses TCP information for routing decisions, then this bug could be triggered.
  • An egress Access Control List (ACL) is applied to an interface and a malformed IP packet that needs to be forwarded through that interface is received.

Note: This list is not exhaustive. It contains some of the scenarios that have been confirmed to trigger the vulnerability described in this document. Other scenarios that require accessing Layer 4 information of a malformed IP packet may also result in the vulnerability being triggered.

Both through-the-device (transit) traffic and to-the-device traffic may trigger this vulnerability. An affected Cisco Nexus switch that has a configured IP address is affected by this vulnerability even if the IP address is used only for management and if the device is configured as a pure Layer 2 switch; that is, no Layer 3 packet forwarding.

When a system reloads because of this vulnerability, a process called "netstack" will terminate unexpectedly, and the following message will be recorded to the system log:

2012 Feb 02 20:32:15 NX-7010 %SYSMGR-2-SERVICE_CRASHED: Service "netstack" (PID 4335)
 hasn't caught signal 11 (core will be saved).

This vulnerability is documented in Cisco Bug IDs CSCti23447 (registered customers only) and CSCti49507 (registered customers only) (Cisco Nexus 1000v and 7000 Series) and CSCtj01991 (registered customers only) (Cisco Nexus 5000 Series), and has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2012-0352.

Note: Two Cisco Bug IDs are used to track this vulnerability in Cisco Nexus 1000v and 7000 Series Switches because the vulnerability was partially fixed by Cisco Bug CSCti23447. The fix was completed with CSCti49507. For the Cisco Nexus 5000 Series Switches, the vulnerability was completely fixed by Cisco Bug CSCtj01991

Vulnerability Scoring Details

Cisco has scored the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this security advisory is in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys vulnerability severity and helps organizations determine the urgency and priority of a response.

Cisco has provided a base and temporal score. Customers can also compute environmental scores that help determine the impact of the vulnerability in their own networks.

Cisco has provided additional information regarding CVSS at the following link:

http://www.cisco.com/web/about/security/intelligence/cvss-qandas.html

Cisco has also provided a CVSS calculator to compute the environmental impact for individual networks at the following link:

http://intellishield.cisco.com/security/alertmanager/cvss

CSCti23447, CSCti49507, CSCtj01991

Calculate the environmental score of CSCti23447, CSCti49507, CSCtj01991
CVSS Base Score - 7.8
Access Vector Access Complexity Authentication Confidentiality Impact Integrity Impact Availability Impact
Network Low None None None Complete
CVSS Temporal Score - 6.4
Exploitability Remediation Level Report Confidence
Functional Official-Fix Confirmed

Impact

Successful exploitation of the vulnerability that is described in this advisory may result in a reload of an affected device. Repeated exploitation could result in a sustained DoS condition.

Software Versions and Fixes

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 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.

Each row of the Cisco NX-OS Software table (below) names a Cisco NX-OS Software release train. If a given release train is vulnerable, then the earliest possible releases that contain the fix (along with the anticipated date of availability for each, if applicable) are listed in the First Fixed Release column of the table. A device that is running a release in the given train that is earlier than the release in a specific column (less than the First Fixed Release) is known to be vulnerable.

Platform Major Release First Fixed Release
Cisco VSG for Nexus 1000V Series Switches 4.x 4.2(1)VSG1(3.1)
Nexus 1000v Series Switches 4.x 4.2(1)SV1(4b) (available late April 2012)

4.2(1)SV1(5.1)

Nexus 1010 Series Switches 4.x
4.2(1)SP1(4)
Nexus 5000 Series Switches 4.x Vulnerable; migrate to 5.x
5.0.x 5.0(2)N1(1)
5.1.x Not vulnerable
Nexus 7000 Series Switches 4.2.x 4.2.8
5.0.x 5.0.5
5.1.x 5.1.1
5.2.x Not vulnerable
6.x Not vulnerable

Cisco NX-OS Software can be downloaded at

http://www.cisco.com/cisco/software/find.html?q=nx-os


Workarounds

There are no workarounds for the vulnerability described in this document.

Obtaining Fixed Software

Cisco has released free software updates that address the vulnerability|vulnerabilities described in this advisory. Prior to deploying software, customers are advised to consult their maintenance providers or check the software for feature set compatibility and known issues that are specific to their environments.

Customers may only install and expect support for feature sets they have purchased. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html, or as set forth at http://www.cisco.com/public/sw-center/sw-usingswc.shtml.

Do not contact psirt@cisco.com or security-alert@cisco.com for software upgrades.

Customers with Service Contracts

Customers with contracts should obtain upgraded software through their regular update channels. For most customers, upgrades should be obtained through the Software Center on Cisco.com at http://www.cisco.com.

Customers Using Third-Party Support Organizations

Customers with Cisco products that are provided or maintained through prior or existing agreements with third-party support organizations, such as Cisco Partners, authorized resellers, or service providers, should contact that organization for assistance with the appropriate course of action.

The effectiveness of any workaround or fix depends on specific customer situations, such as product mix, network topology, traffic behavior, and organizational mission. Because of the variety of affected products and releases, customers should consult their service providers or support organizations to ensure that any applied workaround or fix is the most appropriate in the intended network before it is deployed.

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):

  • +1 800 553 2447 (toll free from within North America)
  • +1 408 526 7209 (toll call from anywhere in the world)
  • e-mail: tac@cisco.com

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. Customers without service contracts should request free upgrades through the TAC.

Refer to Cisco Worldwide Contacts at http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html for additional TAC contact information, including localized telephone numbers, instructions, and e-mail addresses for support in various languages.

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.

This vulnerability was discovered while working on customer support cases.

Status of This Notice: Final

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.


Distribution

This advisory is posted on Cisco Security at the following link:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120215-nxos

Additionally, a text version of this advisory is clear signed with the Cisco PSIRT PGP key and circulated among the following e-mail addresses:

  • cust-security-announce@cisco.com
  • first-bulletins@lists.first.org
  • bugtraq@securityfocus.com
  • vulnwatch@vulnwatch.org
  • cisco@spot.colorado.edu
  • cisco-nsp@puck.nether.net
  • full-disclosure@lists.grok.org.uk

Future updates of this advisory, if any, will reside on Cisco.com but may not be announced on mailing lists. Users can monitor this advisory's URL for any updates.


Revision History

Revision 2.0 2012-March-26 Added Nexus 1010 and VSG as vulnerable products and included fixed software information for them. Added 4.2(1)SV1(4b) as a first fixed release for Nexus 1000v.
Revision 1.1 2012-February-17 Added 4.x releases for Nexus 1000v Series Switches as vulnerable.
Revision 1.0 2012-February-15 Initial public release.

Cisco Security Procedures

Complete information about reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco is available on Cisco.com at http://www.cisco.com/web/about/security/psirt/security_vulnerability_policy.html. This web page includes instructions for press inquiries regarding Cisco Security Advisories. All Cisco Security Advisories are available at http://www.cisco.com/go/psirt.


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