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             AUSCERT External Security Bulletin Redistribution

        Cisco Enterprise NFV Infrastructure Software Authentication
                           Bypass Vulnerability
                             2 September 2021


        AusCERT Security Bulletin Summary

Product:           Enterprise NFV Infrastructure Software (NFVIS)
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Administrator Compromise -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-34746  

Original Bulletin: 

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Cisco Enterprise NFV Infrastructure Software Authentication Bypass

Priority:        Critical
Advisory ID:     cisco-sa-nfvis-g2DMVVh
First Published: 2021 September 1 16:00 GMT
Version 1.0:     Final
Workarounds:     No workarounds available
Cisco Bug IDs:   CSCvz16015
CVE Names:       CVE-2021-34746
CWEs:            CWE-289


  o A vulnerability in the TACACS+ authentication, authorization and accounting
    (AAA) feature of Cisco Enterprise NFV Infrastructure Software (NFVIS) could
    allow an unauthenticated, remote attacker to bypass authentication and log
    in to an affected device as an administrator.

    This vulnerability is due to incomplete validation of user-supplied input
    that is passed to an authentication script. An attacker could exploit this
    vulnerability by injecting parameters into an authentication request. A
    successful exploit could allow the attacker to bypass authentication and
    log in as an administrator to the affected 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:

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco Enterprise NFVIS Release 4.5.1 if the
    TACACS external authentication method is configured.

    Determine TACACS External Authentication Configuration

    To determine if a TACACS external authentication feature is enabled on a
    device, use the show running-config tacacs-server command. The following
    example shows the output of the show running-config tacacs-server command
    on Cisco Enterprise NFVIS when TACACS external authentication is enabled:

        nfvis# show running-config tacacs-server
        tacacs-server host
         key           0
         shared-secret "example!23"
         admin-priv    15
         oper-priv     1

    If the output of the show running-config tacacs-server command is No
    entries found , the TACACS external authentication feature is not enabled.

    Alternatively, check the configuration through the GUI. Choose
    Configuration > Host > Security > User and Roles . If a TACACS+ host is
    defined under External Authentication , the device is considered to be

    Configurations that are using RADIUS or local authentication only are not

    Products Confirmed Not Vulnerable

    Only products listed in the Vulnerable Products section of this advisory
    are known to be affected by this vulnerability.


  o There are no workarounds that address this vulnerability.

Fixed Software

  o 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:

    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 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

    Fixed Releases

    Cisco fixed this vulnerability in Cisco Enterprise NFVIS releases 4.6.1 and

Exploitation and Public Announcements

  o The Cisco Product Security Incident Response Team (PSIRT) is aware that
    proof-of-concept exploit code is available for the vulnerability described
    in this advisory.

    The Cisco PSIRT is not aware of any malicious use of the vulnerability that
    is described in this advisory.


  o Cisco would like to thank Cyrille Chatras of Orange Group for reporting
    this vulnerability.

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.


  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nfvis-g2DMVVh

Revision History

  o +----------+---------------------------+----------+--------+--------------+
    | Version  |        Description        | Section  | Status |     Date     |
    | 1.0      | Initial public release.   | -        | Final  | 2021-SEP-01  |

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