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             AUSCERT External Security Bulletin Redistribution

 Cisco IOS XR Software NETCONF Over Secure Shell ACL Bypass Vulnerability
                             25 November 2019


        AusCERT Security Bulletin Summary

Product:           Cisco IOS XR
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Unauthorised Access -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2019-15998  

Original Bulletin: 

Revision History:  November 25 2019: Vendor updated affected versions &
                                     added instructions for requesting update
                   November 21 2019: Initial Release

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Cisco IOS XR Software NETCONF Over Secure Shell ACL Bypass Vulnerability

Priority:        Medium
Advisory ID:     cisco-sa-20191120-iosxr-ssh-bypass
First Published: 2019 November 20 16:00 GMT
Last Updated:    2019 November 23 02:24 GMT
Version 1.1:     Final
Workarounds:     No workarounds available

Cisco Bug IDs:   CSCvp91299


CVSS Score:


  o A vulnerability in the access-control logic of the NETCONF over Secure
    Shell (SSH) of Cisco IOS XR Software may allow connections despite an
    access control list (ACL) that is configured to deny access to the NETCONF
    over SSH of an affected device.

    The vulnerability is due to a missing check in the NETCONF over SSH access
    control list (ACL). An attacker could exploit this vulnerability by
    connecting to an affected device using NETCONF over SSH. A successful
    exploit could allow the attacker to connect to the device on the NETCONF
    port. Valid credentials are required to access the device. This
    vulnerability does not affect connections to the default SSH process on the

    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

    At the time of publication, this vulnerability affected Cisco IOS XR
    Software releases 6.5.1, 6.5.2, and 6.5.3. This vulnerability does not
    affect any other releases.

    See the Details section in the bug ID(s) at the top of this advisory for
    the most complete and current information.

    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 Cisco IOS
    Software or Cisco IOS XE Software.


  o There are no workarounds that address this vulnerability.

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

    At the time of publication, Cisco IOS XR Software Release 6.5.3 with SMU
    and later contained the fix for this vulnerability.

    See the Details section in the bug ID(s) at the top of this advisory for
    the most complete and current information.

    Customers can download the SMU from the Software Center by doing the

     1. Click Browse all .
     2. Choose Routers > Service Provider Edge Routers .
     3. Choose the specific router family from the right pane of the product
     4. Choose a specific product from the right pane of the product selector.
     5. Choose Software on Chassis > IOS XR Software Maintenance Upgrades (SMU)
        - 6.5.3 .
     6. Click the download link for the Hitless/Optional SMU, ACL under 'ssh
        server netconf' did not take effect release.

    If the SMU is not listed for your required platform, contact your account
    team or the Cisco TAC to request an SMU for your platform.

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       |
    |         | Clarified affected  | Vulnerable  |        |                  |
    | 1.1     | releases. Added     | Products    | Final  | 2019-November-23 |
    |         | instructions for    | and Fixed   |        |                  |
    |         | requesting an SMU.  | Releases    |        |                  |
    | 1.0     | Initial public      | -           | Final  | 2019-November-20 |
    |         | release.            |             |        |                  |

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