Cisco Security AdvisoryHigh
Advisory ID:
cisco-sa-20161005-dhcp1
First Published:
2016 October 5 16:00 GMT
Version 1.0:
Workarounds:
No workarounds available
Cisco Bug IDs:
CVSS Score:
Base 7.8,
Temporal 6.4
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AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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A vulnerability in the implementation of the DHCPv4 relay agent and smart relay agent in Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
The vulnerability is due to improper validation of crafted DHCPv4 offer packets. An attacker could exploit this vulnerability by sending crafted DHCPv4 offer packets to an affected device. An exploit could allow the attacker to cause the DHCP process or device to crash.
This vulnerability can be exploited using IPv4 packets only. The vulnerability can be triggered by crafted DHCP packets processed by a DHCP relay agent or smart relay agent listening on the device using the IPv4 broadcast address or the IPv4 unicast address of any interface configured on a device.
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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161005-dhcp1
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Vulnerable Products
The following Cisco products are vulnerable if they are running Cisco NX-OS System Software that is configured for DHCP:
- Nexus 2000 Series Fabric Extenders
- Nexus 5000 Series 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 Application Centric Infrastructure (ACI) mode
- Nexus 9000 Series Switches in NX-OS mode
To determine whether a Cisco Nexus device that is running a vulnerable version of Cisco NX-OS Software is configured as a DHCPv4 relay agent or smart relay agent, administrators can use the show running | include dhcp command from the Cisco NX-OS command-line interface (CLI) and verify that the feature is enabled.
The following example shows that the DHCP relay feature is enabled on a device running Cisco NX-OS Software that is configured to relay DHCP requests to IPv4 address 192.168.0.1:
# show running | include dhcp feature dhcp
ip dhcp relay ip dhcp relay address 192.168.0.1To determine whether a vulnerable version of software is running on a Cisco NX-OS device, administrators can use the show version command from the Cisco NX-OS CLI. The following example shows the results for a Cisco Nexus 5000 Series Switch running Cisco NX-OS Software version 5.2(1)N1(1b):
# 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 5.2(1)N1(1b)
system: version 5.2(1)N1(1b)Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this vulnerability.
The following products are not affected by this vulnerability:
- Multilayer Director Switches
- Nexus 1000V Series Switches
- Nexus 3000 Series Switches
- Nexus 3500 Platform Switches
- Nexus 4000 Series Switches
- Unified Computing System (UCS) 6100 Series Fabric Interconnects
- UCS 6200 Series Fabric Interconnects
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Exploitation of this vulnerability will cause the affected device to reload and generate a DHCP process core file. Contact the Cisco Technical Assistance Center (TAC) to review the core file and determine whether the device has been compromised by exploitation of this vulnerability.
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There are no workarounds that address this vulnerability.
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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-20161005-bgp: Cisco NX-OS Border Gateway Protocol Denial of Service Vulnerability
cisco-sa-20161005-dhcp1: Cisco NX-OS Software Crafted DHCPv4 Packet Denial of Service Vulnerability
cisco-sa-20161005-dhcp2: Cisco NX-OS Software Malformed DHCPv4 Packet Denial of Service Vulnerability
cisco-sa-20161005-nxaaa: Cisco NX-OS Software-Based Products Authentication, Authorization, and Accounting Bypass Vulnerability
cisco-sa-20161005-otv: Cisco Nexus 7000 and 7700 Series Switches Overlay Transport Virtualization Buffer Overflow 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.
Cisco Nexus 2000, 5000, 5500, 5600, and 6000 Series Switches: CSCus21693
Cisco NX-OS Software
Major Release - Nexus 5000 Series SwitchesFirst Fixed Release for This Vulnerability
First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories Prior to 5.2 Affected; migrate to 5.2(1)N1(9) 5.2(1)N1(9a) 5.2
5.2(1)N1(9)
5.2(1)N1(9a)
Cisco NX-OS Software
Major Release - Nexus 2000, 5500 Platform, 5600 Platform, and 6000 Series SwitchesFirst Fixed Release for This Vulnerability First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories Prior to 5.2 Affected; migrate to 5.2(1)N1(9) 7.1(4)N1(1)
5.2
5.2(1)N1(9)
7.1(4)N1(1)
6.0
6.0(2)N2(7) )
7.1(4)N1(1)
7.0 7.0(6)N1(1) 7.1(4)N1(1) 7.1 7.1(1)N1(1)
7.1(4)N1(1) 7.2 7.2(0)N1(1) 7.2(2)N1(1) 7.3 7.3(0)N1(1) 7.3(0)N1(1)
Cisco Nexus 7000 and 7700 Series Switches: CSCuq24603
Cisco NX-OS Software Major Release - Nexus 7000 and 7700 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 Affected; migrate to 6.2(16)
7.2(2)D1(1) 5.2
Affected; migrate to 6.2(16)
7.2(2)D1(1)
6.0 Affected; migrate to 6.2(16) 7.2(2)D1(1)
6.1 Affected; migrate to 6.2(16) 7.2(2)D1(1) 6.2 6.2(16)
7.2(2)D1(1) 7.2 7.2(0)D1(1) 7.2(2)D1(1)
7.3 7.3(0)D1(1) 7.3(1)D1(1)
Cisco Nexus 9000 Series Switches in ACI Mode: CSCut76171
Cisco NX-OS Software Major Release - Nexus 9000 Series Switches in ACI Mode First Fixed Release for This Vulnerability First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
11.0 Affected; migrate to 11.1(1) 11.1(1j)
11.1 11.1(1)
11.1(1j)
11.2 Not vulnerable Not vulnerable
Cisco Nexus 9000 Series Switches in NX-OS Mode: CSCur93159
Cisco NX-OS Software Major Release - Nexus 9000 Series Switches in NX-OS Mode First Fixed Release for This Vulnerability First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Collection of Advisories
6.1 Affected; migrate to 7.0(3)I1(1)
7.0(3)I4(1) 7.0 7.0(3)I1(1)
7.0(3)I4(1)
Release Recommendations
For additional assistance in determining the best NX-OS Software release for a Cisco Nexus Switch, refer to the recommended release document for the switch:
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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.
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This vulnerability was found during the resolution of a support case.
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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 LessVersion Description Section Status Date 1.0 Initial public release. — Final 2016-October-05
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