Cisco Security Advisory
Cisco NX-OS Malformed IP Packet Denial of Service Vulnerability
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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 software updates that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120215-nxos
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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.
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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
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There are no workarounds for the vulnerability described in this document.
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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
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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.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessRevision 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.
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