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AUSCERT External Security Bulletin Redistribution
ESB-2020.0622
Cisco IOS XR Software Intermediate System-to-Intermediate
System Denial of Service Vulnerability
21 February 2020
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XR Software
Publisher: Cisco Systems
Operating System: Network Appliance
Impact/Access: Denial of Service -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2019-16027
Reference: ESB-2020.0421
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200122-ios-xr-dos
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Cisco IOS XR Software Intermediate System-to-Intermediate System Denial of
Service Vulnerability
Priority: High
Advisory ID: cisco-sa-20200122-ios-xr-dos
First Published: 2020 January 22 16:00 GMT
Last Updated: 2020 February 19 18:42 GMT
Version 1.2: Final
Workarounds: No workarounds availableCisco Bug IDs: CSCvr62342
CVE-2019-16027
CWE-20
CVSS Score:
7.7 AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o A vulnerability in the implementation of the Intermediate
System-to-Intermediate System (IS-IS) routing protocol functionality in
Cisco IOS XR Software could allow an authenticated, remote attacker to
cause a denial of service (DoS) condition in the IS-IS process.
The vulnerability is due to improper handling of a Simple Network
Management Protocol (SNMP) request for specific Object Identifiers (OIDs)
by the IS-IS process. An attacker could exploit this vulnerability by
sending a crafted SNMP request to the affected device. A successful exploit
could allow the attacker to cause a DoS condition in the IS-IS process.
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-20200122-ios-xr-dos
Affected Products
o Vulnerable Products
This vulnerability affects Cisco devices if they are running Cisco IOS XR
Software releases earlier than 6.6.3, 7.0.2, 7.1.1, or 7.2.1 and they
configured with both the IS-IS routing protocol and SNMP versions 1, 2c, or
3.
Cisco has confirmed that this vulnerability affects both Cisco IOS XR
32-bit Software and Cisco IOS XR 64-bit Software.
Determine Whether the Device Has a Vulnerable Configuration
To determine if the device is configured for IS-IS routing, administrators
can use the show running-config router isis EXEC command in the CLI. If the
device is configured for IS-IS routing, this command will return output.
The following example shows the partial output of the show running-config
router isis command on a device that is configured for IS-IS routing.
#show running-config router isis
router isis {isp}
is-type level-2-only
...
To determine if the device is configured for SNMP, administrators can use
the show running-config snmp EXEC command in the CLI. If the device is
configured for SNMP, this command will return output. The following
examples show the partial output of the show running-config snmp command on
a device that is configured for SNMP. Only one version of SNMP needs to be
configured for the device to be vulnerable. The vulnerability is triggered
through an SNMP query, but the configuration can be for read or write.
SNMPv1
#show running-config snmp
snmp-server community {public ro}
...
SNMPv2
#show running-config snmp
snmp-server group {SNMP_GROUP1} v2c
...
SNMPv3
#show running-config snmp
snmp-server view {SNMP_VIEW1 1.3.6.1.2.1.1.5 included}
snmp-server group {SNMP_GROUP1} v3 {auth read SNMP_VIEW1}
...
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:
Cisco IOS and IOS XE Software
Cisco IOS XR7-LNT Software
Cisco NX-OS Software
Workarounds
o There are no workarounds that address this vulnerability. However,
administrators may choose to perform one of the following mitigations:
Disable SNMP: This vulnerability is exploited by doing an SNMP query of a
special MIB OID range. If SNMP is disabled, this vulnerability cannot be
exploited. For mitigation of this vulnerability if SNMP is enabled on the
device, contact Cisco TAC for assistance with the OIDs.
Configure an access control list: Administrators can also configure an
access control list (ACL) on an SNMP community to filter incoming SNMP
requests to ensure that SNMP queries are performed only by trusted SNMP
clients. For information about configuring ACLs, see the Cisco Guide to
Harden Cisco IOS XR Devices .
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:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
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 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.
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/en/us/support/web/tsd-cisco-worldwide-contacts.html
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
upgrade.
Fixed Releases
Cisco fixed this vulnerability in Cisco IOS XR Software Release 6.6.3.
Cisco also plans to fix this vulnerability in Cisco IOS XR Software
releases 7.0.2, 7.1.1, and 7.2.1.
Customers are advised to install the appropriate SMU as shown in the
following table. Customers who require SMUs for other platforms and
releases are advised to contact their support organization.
IOS XR Release Platform SMU Name
4.3.2 XR12000 c12k-4.3.2.CSCvr62342
5.2.5 NCS6K ncs6k-5.2.5.CSCvr62342
6.1.2 ASR9K-PX asr9k-px-6.1.2.CSCvr62342
6.1.3 ASR9K-PX asr9k-px-6.1.3.CSCvr62342
6.1.3 NCS5K ncs5k-6.1.3.CSCvr62342
6.1.3 NCS5500 ncs5500-6.1.3.CSCvr62342
6.1.4 ASR9K-PX asr9k-px-6.1.4.CSCvr6234
6.1.4 CRS-PX hfr-px-6.1.4.CSCvr62342
6.1.4 NCS5500 ncs5500-6.1.4.CSCvr62342
6.1.4 NCS5K ncs5k-6.1.4.CSCvr62342
6.1.4 XRV9K xrv9k-6.1.4.CSCvr62342
6.2.2 ASR9K-PX asr9k-px-6.2.2.CSCvr62342
6.2.2 NCS6K ncs6k-6.2.2.CSCvr62342
6.2.25 NCS5K ncs5k-6.2.25.CSCvr62342
6.2.25 NCS6K ncs6k-6.2.25.CSCvr62342
6.2.3 NCS5K ncs5k-6.2.3.CSCvr62342
6.2.3 ASR9K-PX asr9k-px-6.2.3.CSCvr62342
6.2.3 ASR9K-X64 asr9k-x64-6.2.3.CSCvr62342
6.2.3 CRS-PX hfr-px-6.2.3.CSCvr62342
6.2.3 NCS5500 ncs5500-6.2.3.CSCvr62342
6.2.3 XRV9K xrv9k-6.2.3.CSCvr62342
6.2.3 NCS6K ncs6k-6.2.3.CSCvr62342
6.3.15 NCS5500 ncs5500-6.3.15.CSCvr62342
6.3.2 ASR9K-PX asr9k-px-6.3.2.CSCvr62342
6.3.2 ASR9K-X64 asr9k-x64-6.3.2.CSCvr62342
6.3.3 ASR9K-X64 asr9k-x64-6.3.3.CSCvr62342
6.3.3 ASR9K-PX asr9k-px-6.3.3.CSCvr62342
6.3.3 NCS5K ncs5k-6.3.3.CSCvr62342
6.3.3 NCS540 ncs540-6.3.3.CSCvr62342
6.3.3 NCS5500 ncs5500-6.3.3.CSCvr62342
6.3.3 NCS6K ncs6k-6.3.3.CSCvr62342
6.4.2 ASR9K-PX asr9k-px-6.4.2.CSCvr62342
6.4.2 ASR9K-X64 asr9k-x64-6.4.2.CSCvr62342
6.4.2 CRS-PX hfr-px-6.4.2.CSCvr62342
6.4.2 NCS5K ncs5k-6.4.2.CSCvr62342
6.4.2 NCS6K ncs6k-6.4.2.CSCvr62342
6.4.2 XRV9K xrv9k-6.4.2.CSCvr62342
6.5.2 ASR9K-PX asr9k-px-6.5.2.CSCvr62342
6.5.2 ASR9K-X64 asr9k-x64-6.5.2.CSCvr62342
6.5.2 NCS5K ncs5k-6.5.2.CSCvr62342
6.5.2 NCS5500 ncs5500-6.5.2.CSCvr62342
6.5.3 ASR9K-X64 asr9k-x64-6.5.3.CSCvr62342
6.5.3 NCS5500 ncs5500-6.5.3.CSCvr62342
6.5.3 NCS540 ncs540-6.5.3.CSCvr62342
6.5.3 NCS5K ncs5k-6.5.3.CSCvr62342
6.5.3 ASR9K-PX asr9k-px-6.5.3.CSCvr62342
6.5.3 XRV9K xrv9k-6.5.3.CSCvr62342
6.6.1 NCS5500 ncs5500-6.6.1.CSCvr62342
6.6.2 ASR9K-PX asr9k-px-6.6.2.CSCvr62342
6.6.2 ASR9K-X64 asr9k-x64-6.6.2.CSCvr62342
6.6.2 XRV9K xrv9k-6.6.2.CSCvr62342
6.6.25 NCS5500 ncs5500-6.6.25.CSCvr62342
6.6.25 NCS540 ncs540-6.6.25.CSCvr62342
6.6.25 NCS560 ncs560-6.6.25.CSCvr62342
To download the SMUs from the Software Center on Cisco.com , do the
following:
1. Click Browse All .
2. Choose IOS and NX-OS Software > IOS XR > IOS XR Software > Optical
Networking or Routers .
3. Choose a specific product and model from the right pane of the product
selector.
4. Choose a release from the left pane of the product page.
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.
Action Links for This Advisory
o Snort Rule 52645
Snort Rule 52646
Snort Rule 52647
Snort Rule 52648
Snort Rule 52649
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-20200122-ios-xr-dos
Revision History
o +---------+---------------------+-------------+--------+------------------+
| Version | Description | Section | Status | Date |
+---------+---------------------+-------------+--------+------------------+
| | Updated Fixed | Fixed | | |
| 1.2 | Releases table to | Releases | Final | 2020-February-19 |
| | add current SMUs. | | | |
+---------+---------------------+-------------+--------+------------------+
| | Changed en dashes | Title, | | |
| | to hyphens | Summary, | | |
| 1.1 | throughout. No | and | Final | 2020-February-04 |
| | content changes | Vulnerable | | |
| | were made. | Products. | | |
+---------+---------------------+-------------+--------+------------------+
| 1.0 | Initial public | - | Final | 2020-January-22 |
| | release. | | | |
+---------+---------------------+-------------+--------+------------------+
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