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AUSCERT External Security Bulletin Redistribution
ESB-2019.4402.2
Cisco IOS XR Software NETCONF Over Secure Shell ACL Bypass Vulnerability
25 November 2019
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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:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191120-iosxr-ssh-bypass
Revision History: November 25 2019: Vendor updated affected versions &
added instructions for requesting update
November 21 2019: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
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
CVE-2019-15998
CWE-284
CVSS Score:
5.3 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:X/RL:X/RC:X
Summary
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
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:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-20191120-iosxr-ssh-bypass
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.
Workarounds
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
providers.
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
following:
1. Click Browse all .
2. Choose Routers > Service Provider Edge Routers .
3. Choose the specific router family from the right pane of the product
selector.
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.
Source
o This vulnerability was found during the resolution of a Cisco TAC support
case.
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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-20191120-iosxr-ssh-bypass
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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