Summary

• A vulnerability in the OSPF version 3 (OSPFv3) feature of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

  This vulnerability is due to incomplete input validation of specific OSPFv3 packets. An attacker could exploit this vulnerability by sending a malicious OSPFv3 link-state advertisement (LSA) to an affected device. A successful exploit could allow the attacker to cause the OSPFv3 process to crash and restart multiple times, causing the affected device to reload and resulting in a DoS condition.

  Note: The OSPFv3 feature is disabled by default. To exploit this vulnerability, an attacker must be able to establish a full OSPFv3 neighbor state with an affected device. For more information about exploitation conditions, see the Details section of this advisory.

  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-nxos-ospfv3-dos-48qutcu

  This advisory is part of the August 2022 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: August 2022 Semiannual Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco NX-OS Software and are configured for OSPFv3 routing on at least one interface:

  • Nexus 3000 Series Switches (CSCvz68748)
  • Nexus 5500 Platform Switches (CSCwb50015)
  • Nexus 5600 Platform Switches (CSCwb50015)
  • Nexus 6000 Series Switches (CSCwb50015)
  • Nexus 7000 Series Switches (CSCwb50013)
  • Nexus 9000 Series Fabric Switches in ACI mode (CSCwb50012)
  • Nexus 9000 Series Switches in standalone NX-OS mode (CSCvz68748)

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

  Determine the Status of OSPFv3

  The OSPFv3 feature is disabled by default. To determine whether a device is configured with the OSPFv3 feature enabled, use the show feature | include ospfv3 command from the Cisco NX-OS CLI and verify that the feature is enabled. The following example shows the OSPFv3 feature enabled on a device that is running Cisco NX-OS Software:

  nxos# show feature | include ospfv3
  ospfv3                1        enabled

  To determine whether a device is configured with OSPFv3 enabled on at least one interface, use the show running-config | include "ipv6 router ospfv3" command from the Cisco NX-OS CLI. If the command returns at least one line, OSPFv3 is enabled on at least one interface:

  nxos# show running-config | include "ipv6 router ospfv3"
    ipv6 router ospfv3 101 area 0.0.0.0

  To determine whether a device has any OSPFv3 neighbors in FULL state, use the show ipv6 ospfv3 neighbors command from the Cisco NX-OS CLI, as shown in the following example:

  nxos# show ipv6 ospfv3 neighbors 
   OSPFv3 Process ID 101 VRF default
   Total number of neighbors: 1
   Neighbor ID     Pri State            Up Time  Interface ID    Interface
   10.3.3.3           1 FULL/DR          02:11:53 107             Eth1/1 
     Neighbor address fe80::1ae7:28ff:fedb:407f

  
  

  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 1000 Series
  • Firepower 2100 Series
  • Firepower 4100 Series
  • Firepower 9300 Security Appliances
  • MDS 9000 Series Multilayer Switches
  • Nexus 1000 Virtual Edge for VMware vSphere
  • Nexus 1000V Switch for Microsoft Hyper-V
  • Nexus 1000V Switch for VMware vSphere
  • UCS 6200 Series Fabric Interconnects
  • UCS 6300 Series Fabric Interconnects
  • UCS 6400 Series Fabric Interconnects

Details

• The OSPFv3 implementation on Cisco NX-OS Software only supports the transport of IPv6 routing information and requires an IPv6 address to be configured on any interface enabled for OSPFv3 routing.

  To exploit this vulnerability, an attacker must be able to establish a full OSPFv3 neighbor state with an affected device. This requires the attacker to use OSPFv3 parameters that are compatible with the affected device, including valid authentication information if OSPFv3 authentication is configured on the device.

  A device running OSPFv3 may communicate with a neighbor that is one or more Layer 3 hops away only if a virtual link to such neighbor is explicitly configured on the device. If no OSPFv3 virtual link is configured, an attacker must be Layer 2 adjacent to the affected device to exploit this vulnerability.

Workarounds

• There are no workarounds that address this vulnerability.

  However, OSPFv3 authentication can be used to reduce the attack surface by allowing only authenticated peers to establish a full OSPFv3 neighbor state. OSPFv3 authentication is supported on Nexus 3000 and Nexus 7000 Series Switches and on Nexus 9000 Series Switches in standalone NX-OS mode. It is not currently supported on Nexus 5500 and Nexus 5600 Platform Switches, Nexus 6000 Series Switches and Nexus 9000 Series Fabric Switches in ACI mode.

  While this mitigation has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

Fixed Software

• Cisco has released free software updates that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.

  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.

  The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.

  When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories 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.

  Cisco NX-OS Software

  To help customers determine their exposure to vulnerabilities in Cisco NX-OS Software, Cisco provides the Cisco Software Checker. This tool identifies any Cisco security advisories that impact a specific software release and the earliest release that fixes the vulnerabilities that are described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories that the Software Checker identifies (“Combined First Fixed”).

  To use the tool, go to the Cisco Software Checker page and follow the instructions. Alternatively, use the following form to search for vulnerabilities that affect a specific software release. To use the form, follow these steps:

  1. Choose which advisories the tool will search-only this advisory, only advisories with a Critical or High Security Impact Rating (SIR), or all advisories.
  2. Choose the appropriate software.
  3. Choose the appropriate platform.
  4. Enter a release number-for example, 7.0(3)I7(5) for Cisco Nexus 3000 Series Switches or 14.0(1h) for Cisco NX-OS Software in ACI mode.
  5. Click Check.

  
  

  Only this advisory All Critical and High advisories All advisories Cisco NX-OS Software Cisco NX-OS Software in ACI Mode Any Platform MDS 9000 Series Multilayer Switches Nexus 1000V Series Switches Nexus 3000 Series Switches Nexus 5000 Series Switches Nexus 6000 Series Switches Nexus 7000 Series Switches Nexus 9000 Series Switches

  
  

  Cisco Nexus 7000 Series Switches SMUs

  Cisco has released the following SMUs to address this vulnerability. Customers can download the SMUs from the Software Center on Cisco.com.

  Cisco NX-OS Software Release	Platform	SMU Name
  8.2(8)	Nexus 7000 Series Switches	n7000-s2-dk9.8.2.8.CSCwc36631.bin n7700-s2-dk9.8.2.8.CSCwc36631.bin

  For details about downloading and installing SMUs in Cisco NX-OS Software for Cisco Nexus 7000 Series Switches, see the Performing Software Maintenance Upgrades section of the Cisco NX-OS system management configuration guide for Cisco Nexus 7000 Series Switches.

  Additional Resources

  For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

  Cisco MDS Series Switches
  Cisco Nexus 1000V for VMware Switch
  Cisco Nexus 3000 Series Switches
  Cisco Nexus 5500 Platform Switches
  Cisco Nexus 5600 Platform Switches
  Cisco Nexus 6000 Series Switches
  Cisco Nexus 7000 Series Switches
  Cisco Nexus 9000 Series Switches
  Cisco Nexus 9000 Series ACI-Mode Switches

  To determine the best release for Cisco UCS Software, see the Recommended Releases documents in the release notes for the device.

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.

Source

• This vulnerability was found by Sivasankar Sundararaj of Cisco during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-ospfv3-dos-48qutcu

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2022-AUG-24

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