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             AUSCERT External Security Bulletin Redistribution

        Cisco NX-OS Software OSPFv3 Denial of Service Vulnerability
                              25 August 2022


        AusCERT Security Bulletin Summary

Product:           Cisco NX-OS Software
Publisher:         Cisco Systems
Operating System:  Cisco
Resolution:        Patch/Upgrade
CVE Names:         CVE-2022-20823  

Original Bulletin: 

Comment: CVSS (Max):  8.6 CVE-2022-20823 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
         CVSS Source: Cisco Systems
         Calculator:  https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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Cisco NX-OS Software OSPFv3 Denial of Service Vulnerability

Priority:        High
Advisory ID:     cisco-sa-nxos-ospfv3-dos-48qutcu
First Published: 2022 August 24 16:00 GMT
Version 1.0:     Final
Workarounds:     No workarounds available
Cisco Bug IDs:   CSCvz68748 CSCwb50012 CSCwb50013 CSCwb50015
CVE Names:       CVE-2022-20823
CWEs:            CWE-126


  o 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:

    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

  o 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

    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           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


  o 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


  o 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

Fixed Software

  o 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:

    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

    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

    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

    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

    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.

    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  Platform            SMU Name
    8.2(8)                Nexus 7000 Series   n7000-s2-dk9.8.2.8.CSCwc36631.bin
                          Switches            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

  o 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.


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

Cisco Security Vulnerability Policy

  o 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.

Related to This Advisory

  o Cisco Event Response: August 2022 Semiannual Cisco FXOS and NX-OS Software
    Security Advisory Bundled Publication


  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-ospfv3-dos-48qutcu

Revision History

  o +----------+---------------------------+----------+--------+--------------+
    | Version  |        Description        | Section  | Status |     Date     |
    | 1.0      | Initial public release.   | -        | Final  | 2022-AUG-24  |

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