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             AUSCERT External Security Bulletin Redistribution

 Cisco IOS XR Software Standby Route Processor Gigabit Ethernet Management
            Interface Access Control List Bypass Vulnerability
                               18 June 2020


        AusCERT Security Bulletin Summary

Product:           Cisco IOS XR Software
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Unauthorised Access -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2020-3364  

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

Cisco IOS XR Software Standby Route Processor Gigabit Ethernet Management
Interface Access Control List Bypass Vulnerability

Priority:        Medium

Advisory ID:     cisco-sa-xracl-zbWSWREt

First Published: 2020 June 17 16:00 GMT

Version 1.0:     Final

Workarounds:     No workarounds availableCisco Bug IDs:   CSCvt55079



CVSS Score:


  o A vulnerability in the access control list (ACL) functionality of the
    standby route processor management interface of Cisco IOS XR Software could
    allow an unauthenticated, remote attacker to reach the configured IP
    addresses on the standby route processor management Gigabit Ethernet
    Management interface.

    The vulnerability is due to a logic error that was introduced in the Cisco
    IOS XR Software, which prevents the ACL from working when applied against
    the standby route processor management interface. An attacker could exploit
    this vulnerability by attempting to access the device through the standby
    route processor management interface.

    There are no workarounds that address this vulnerability.

    This advisory is available at the following link:

Affected Products

  o Vulnerable Products

    At the time of publication, this vulnerability affected Cisco devices if
    they were running a vulnerable release of Cisco IOS XR Software and had
    dual route processors and an ACL configured on the standby route processor
    management interface.

    At the time of publication, the release information in the following table
    (s) was accurate. See the Details section in the bug ID(s) at the top of
    this advisory for the most complete and current information.

    Cisco IOS XR Software Train                Affected Releases
    6.7                                        6.7.1
    7.0                                        7.0.2, 7.0.11, 7.0.12
    7.1                                        7.1.1, 7.1.15

    Products Confirmed Not Vulnerable

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


  o This vulnerability applies to both IPv4 and IPv6 ACLs.


  o There are no workarounds that address this vulnerability.

    However, administrators can choose one of the following mitigation options
    to help decrease any attack surface:

    For features that leverage the TTYs, apply an ACL to all VTY lines. This
    will mitigate this vulnerability for those applications, as shown in the
    following example:

        line template vty
         access-class ingress MGMT_ACL_V4
        vty-pool default 0 9 line-template vty

    For features that leverage a feature-specific ACL, apply an ACL to the
    feature itself. This will mitigate this vulnerability for those
    applications as shown in the following examples:


        ssh server netconf ipv4 access-list MGMT_ACL_V4


        ssh server ipv4 access-list MGMT_ACL_V4


        telnet ipv4 server max-servers 3 access-list MGMT_ACL_V4

    For features that are controlled through management plane protection, apply
    an out-of-band management plane protection policy, as shown in the
    following example:

           interface MgmtEth0/RSP0/CPU0/0
            allow all peer
             address ipv4
           interface MgmtEth0/RSP1/CPU0/0
            allow all peer
             address ipv4

    Note: Applications that are accessible on the device that do not require a
    TTY to be allocated and do not support application-specific ACLs are still

Fixed Software

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

    Fixed Releases

    For information about fixed software releases, see the Details section in
    the bug ID(s) at the top of this advisory.

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 during the resolution of a Cisco TAC support

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/

Revision History

  o +----------+---------------------------+----------+--------+--------------+
    | Version  |        Description        | Section  | Status |     Date     |
    | 1.0      | Initial public release.   | -        | Final  | 2020-JUN-17  |

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