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AUSCERT External Security Bulletin Redistribution
ESB-2018.1815.2
Cisco Nexus 3000 and 9000 Series CLI and Simple Network Management Protocol
Polling Denial of Service Vulnerability
6 July 2018
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco Nexus 3000 Series
Cisco Nexus 9000 Series
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2018-0309
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180620-n3k-n9k-clisnmp
Revision History: July 6 2018: Updated the Indicators of Compromise section
to describe how to check system memory.
June 21 2018: Initial Release
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco Nexus 3000 and 9000 Series CLI and Simple Network Management Protocol
Polling Denial of Service Vulnerability
Severity: High
Advisory ID: cisco-sa-20180620-n3k-n9k-clisnmp
First Published: 2018 June 20 16:00 GMT
Last Updated: 2018 July 5 21:11 GMT
Version 1.3: Final
Workarounds: No workarounds available
CVSS Score:
Base 7.7
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
*
A vulnerability in the implementation of a specific CLI command and the
associated Simple Network Management Protocol (SNMP) MIB for Cisco Nexus
3000 and 9000 Series Switches could allow an authenticated, remote attacker
to exhaust system memory on an affected device, resulting in a denial of
service (DoS) condition.
The vulnerability is due to the incorrect implementation of the CLI
command, resulting in a failure to free all allocated memory upon
completion. An attacker could exploit this vulnerability by authenticating
to the affected device and repeatedly issuing a specific CLI command or
sending a specific SNMP poll request for a specific Object Identifier
(OID). A successful exploit could allow the attacker to cause the IP
routing process to restart or to cause a device reset, resulting in a DoS
condition.
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-20180620-n3k-n9k-clisnmp
This advisory is part of the June 2018 Cisco FXOS and NX-OS Software
Security Advisory Collection, which includes 24 Cisco Security Advisories
that describe 24 vulnerabilities. For a complete list of the advisories and
links to them, see Cisco Event Response: June 2018 Cisco FXOS and NX-OS
Software Security Advisory Collection.
Affected Products
*
+----------------------------------------------------------------------------------------------------------+
| {INSERT DDTSID} |
| |
| Calculate the environmental score of {INSERT DDTSID} |
|----------------------------------------------------------------------------------------------------------|
| CVSS Base Score - {INSERT BASE SCORE} |
|----------------------------------------------------------------------------------------------------------|
| Attack | Attack | Privileges | User | Scope | Confidentiality | Integrity | Availability |
| Vector | Complexity | Required | Interaction | | Impact | Impact | Impact |
|---------+-------------+------------+--------------+---------+-----------------+-----------+--------------|
| {INSERT | {INSERT | {INSERT | {INSERT USER | {INSERT | {INSERT | {INSERT | {INSERT |
| VECTOR} | ATTACK | PRIVILEGES | INTERACTION} | SCOPE} | CONFIDENTIALITY | INTEGRITY | AVAILABILITY |
| | COMPLEXITY} | REQUIRED} | | | IMPACT} | IMPACT} | IMPACT} |
|----------------------------------------------------------------------------------------------------------|
| CVSS Temporal Score - {INSERT TEMPORAL SCORE} |
|----------------------------------------------------------------------------------------------------------|
| Exploit Code Maturity | Remediation Level | Report Confidence |
|-----------------------+-------------------------------------+--------------------------------------------|
| {INSERT EXPLOIT CODE | {INSERT REMEDIATION LEVEL} | {INSERT REPORT CONFIDENCE} |
| MATURITY} | | |
+----------------------------------------------------------------------------------------------------------+
Vulnerable Products
This vulnerability affects Cisco Nexus 3000 Series Switches and Cisco Nexus
9000 Series Switches in standalone NX-OS mode if they are running a
vulnerable release of Cisco NX-OS Software.
For information about which Cisco NX-OS Software releases are vulnerable,
see the Fixed Software section of this advisory.
Checking the Status of SNMP
Administrators can check whether SNMP is running on a device by using the
show running-config snmp command on the device CLI. If the command returns
output, SNMP is configured.
nxos-switch# show running-config snmp
!Command: show running-config snmp
.
.
.
snmp-server user admin network-admin auth md5 ***** priv ***** localizedkey
snmp-server community <removed> group network-admin
Determining the Cisco NX-OS Software Release
Administrators can check the release of Cisco NX-OS Software that is
running on a device by using the show version command in the device CLI.
The following example shows the output of the command for a device that is
running Cisco NX-OS Software Release 7.0(3)I5(1):
nxos-switch# show version
Cisco Nexus Operating System (NX-OS) Software
TAC support: http://www.cisco.com/tac
Copyright (C) 2002-2016, Cisco and/or its affiliates.
All rights reserved.
The copyrights to certain works contained in this software are
owned by other third parties and used and distributed under their own
licenses, such as open source. This software is provided "as is," and unless
otherwise stated, there is no warranty, express or implied, including but not
limited to warranties of merchantability and fitness for a particular purpose.
Certain components of this software are licensed under
the GNU General Public License (GPL) version 2.0 or
GNU General Public License (GPL) version 3.0 or the GNU
Lesser General Public License (LGPL) Version 2.1 or
Lesser General Public License (LGPL) Version 2.0.
A copy of each such license is available at
http://www.opensource.org/licenses/gpl-2.0.php and
http://opensource.org/licenses/gpl-3.0.html and
http://www.opensource.org/licenses/lgpl-2.1.php and
http://www.gnu.org/licenses/old-licenses/library.txt.
Software
BIOS: version 07.57
NXOS: version 7.0(3)I5(1) [build 7.0(3)I5(0.9)]
BIOS compile time: 06/29/2016
NXOS image file is: bootflash:///nxos.7.0.3.I5.0.9.bin
NXOS compile time: 8/1/2016 23:00:00 [08/02/2016 00:30:32]
.
.
.
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:
+ Firepower 2100 Series
+ Firepower 4100 Series Next-Generation Firewall
+ Firepower 9300 Security Appliance
+ MDS 9000 Series Multilayer Switches
+ Nexus 1000V Series Switches
+ Nexus 1100 Series Cloud Services Platforms
+ Nexus 2000 Series Switches
+ Nexus 3500 Platform Switches
+ Nexus 3600 Platform Switches
+ Nexus 5500 Platform Switches
+ Nexus 5600 Platform Switches
+ Nexus 6000 Series Switches
+ Nexus 7000 Series Switches
+ Nexus 7700 Series Switches
+ Nexus 9000 Series Fabric Switches in Application Centric Infrastructure
(ACI) mode
+ Nexus 9500 R-Series Line Cards and Fabric Modules
+ UCS 6100 Series Fabric Interconnects
+ UCS 6200 Series Fabric Interconnects
+ UCS 6300 Series Fabric Interconnects
Cisco has not investigated whether this vulnerability affects Cisco Nexus
4000 Series Switches, Cisco Nexus 5010 Switches, or Cisco Nexus 5020
Switches because those products have reached end-of-life status. For more
information, refer to the End-of-Sale and End-of-Life Announcement for the
Cisco Nexus 4000 Series Switch Modules for IBM BladeCenter and the
End-of-Sale and End-of-Life Announcement for the Cisco Nexus 5010 and Nexus
5020 Switches.
Details
*
The Simple Network Management Protocol (SNMP) is an application-layer
protocol that provides a standardized framework and a common language for
monitoring and managing devices in a network. It defines a message format
for communication between SNMP managers and agents.
An SNMP agent gathers data from the SNMP MIB, which is the repository of
information about device parameters and network data. It also responds to
requests from an SNMP manager to get or set data. An SNMP agent contains
MIB variables for which values can be requested or changed by an SNMP
manager by using get or set operations.
This vulnerability affects all versions of SNMP supported on the
device?Versions 1, 2c, and 3. An attacker could exploit this vulnerability
by sending a specific SNMP packet to an affected device via IPv4 or IPv6.
Only traffic directed to the affected system can be used to exploit this
vulnerability.
To exploit this vulnerability via SNMP Version 2c or earlier, the attacker
must know the SNMP read-only community string for the affected system. A
community string is a password that is applied to a device to restrict both
read-only and read-write access to the SNMP data on the device. These
community strings, as with all passwords, should be chosen carefully to
ensure that they are not trivial. They should also be changed at regular
intervals and in accordance with network security policies. For example,
the strings should be changed when a network administrator changes roles or
leaves the organization.
To exploit this vulnerability via SNMP Version 3, the attacker must have
user credentials for the affected system.
To exploit this vulnerability, the attacker must take time to repeatedly
send a specific CLI command or send a specific SNMP poll request for a
specific OID to the affected device. Therefore, the attacker cannot
immediately exhaust system memory; instead, system resources would be
consumed over time.
Indicators of Compromise
* Exploitation of this vulnerability could exhaust system memory. The
administrator can monitor the IPFIB process memory usage using the show
process memory | include ipfib | PID command. If an ongoing increase is
observed in the total amount of memory allocated to the IPFIB process,
contact the Cisco Technical Assistance Center (TAC) to help determine if a
proactive reboot of the device is needed:
# show process memory | include ipfib | PID
PID MemAlloc MemLimit MemUsed StackBase/Ptr Process
25179 71282688 1181531648 487817216 ffaf2ca0/ffaf1d9c ipfib
26561 352071680 0 905453568 ff9a87a0/ff9a78a0 ipfib
# show processes memory | include ipfib | PID
PID MemAlloc MemLimit MemUsed StackBase/Ptr Process
25179 71282688 1181531648 487817216 ffaf2ca0/ffaf1d9c ipfib
26561 358326272 0 911708160 ff9a87a0/ff9a78a0 ipf
In addition, exploitation of this vulnerability could cause an affected
device to reload and generate an IPFIB core file. To view the IPFIB core
file, administrators can use the show core command in the NX-OS CLI.
Contact the Cisco TAC to review the core file and determine whether the
device has been compromised by exploitation of this vulnerability.
Workarounds
* There are no workarounds that address this vulnerability.
As a mitigation for the vulnerability that is described in this advisory,
administrators can configure an access control list (ACL) on an SNMP
community to filter incoming SNMP requests to ensure that SNMP polling is
performed only by trusted SNMP clients. In the following example, the
device will accept incoming SNMP requests only from a single trusted host,
192.168.1.2:
switch# show access-list acl_for_snmp
IPV4 ACL acl_for_snmp
10 permit udp 192.168.1.2/32 192.168.1.3/32 eq snmp
To implement the preceding ACL, administrators can add it to the
snmp-server community configuration command:
switch# show running-config snmp
!Command: show running-config snmp
snmp-server community mycompany
use-acl acl_for_snmp
For additional information about configuring ACLs to filter incoming SNMP
requests, see Filtering SNMP Requests in the NX-OS Configuration Guide.
Fixed Software
* 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
Customers are advised to upgrade to an appropriate release as indicated in
the applicable table in this section. To help ensure a complete upgrade
solution, consider that this advisory is part of a collection. For a
complete list of the advisories in the collection and links to them, see
Cisco Event Response: June 2018 Cisco FXOS and NX-OS Software Security
Advisory Collection.
In the following tables, the left column lists releases of Cisco FXOS or
NX-OS Software. The center column indicates whether a release is affected
by the vulnerability described in this advisory and the first release that
includes the fix for this vulnerability. The right column indicates whether
a release is affected by all the vulnerabilities described in this
collection of advisories and which release includes fixes for those
vulnerabilities.
Nexus 3000 Series Switches and Nexus 9000 Series Switches in standalone
NX-OS mode: CSCvf23136
Cisco NX-OS First Fixed Release First Fixed Release for All
Software for This Vulnerabilities Described in the
Release Vulnerability Collection of Advisories
Prior to 7.0 Not vulnerable 7.0(3)I7(4)
(3)I4
7.0(3)I4 7.0(3)I4(8) 7.0(3)I7(4)
7.0(3)I5 7.0(3)I6(2) 7.0(3)I7(4)
7.0(3)I6 7.0(3)I6(2) 7.0(3)I7(4)
7.0(3)I7 7.0(3)I7(1) 7.0(3)I7(4)
Exploitation and Public Announcements
* 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
* This vulnerability was found during the resolution of a Cisco TAC support
case.
Cisco Security Vulnerability Policy
* 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.
Subscribe to Cisco Security Notifications
* Subscribe
Related to This Advisory
* Cisco Event Response: June 2018 Cisco FXOS and NX-OS Software Security
Advisory Collection
URL
* https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-20180620-n3k-n9k-clisnmp
Revision History
*
+-----------------------------------------------------------------------------+
| Version | Description | Section | Status | Date |
|---------+------------------------------+------------+--------+--------------|
| | Updated the Indicators of | Indicators | | |
| 1.3 | Compromise section to | of | Final | 2018-July-05 |
| | describe how to check system | Compromise | | |
| | memory. | | | |
|---------+------------------------------+------------+--------+--------------|
| 1.2 | Metadata update. | ? | Final | 2018-June-26 |
|---------+------------------------------+------------+--------+--------------|
| 1.1 | Metadata update. | ? | Final | 2018-June-26 |
|---------+------------------------------+------------+--------+--------------|
| 1.0 | Initial public release. | ? | Final | 2018-June-20 |
+-----------------------------------------------------------------------------+
- -------------------------------------------------------------------------------
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* THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND
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A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information
or contain factual errors. The information in this document is intended for
end users of Cisco products.
- --------------------------END INCLUDED TEXT--------------------
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