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AUSCERT External Security Bulletin Redistribution
ESB-2017.0296
Cisco ASR 1000 Series Aggregation Services Routers SNMP High
CPU Denial of Service Vulnerability
2 February 2017
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco ASR 1000 Series Router
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2017-3820
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170201-asrsnmp
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Cisco Security Advisory
Cisco ASR 1000 Series Aggregation Services Routers SNMP High CPU Denial of
Service Vulnerability
Medium
Advisory ID:
cisco-sa-20170201-asrsnmp
First Published:
2017 February 1 16:00 GMT
Version 1.0:
Final
Workarounds:
Yes
Cisco Bug IDs:
CSCux68796
CVE-2017-3820
CWE-399
CVSS Score:
Base 6.5, Temporal 6.5[blue-squar]Click Icon to Copy Verbose Score
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:X/RL:X/RC:X
CVE-2017-3820
CWE-399
Download CVRF
Download PDF
Email
Summary
A vulnerability in Simple Network Management Protocol (SNMP) functions of
Cisco ASR 1000 Series Aggregation Services Routers running Cisco IOS XE
Software Release 3.13.6S, 3.16.2S, or 3.17.1S could allow an authenticated,
remote attacker to cause high CPU usage on an affected device, resulting in
a denial of service (DoS) condition.
The vulnerability is due to an incorrect initialized variable. An attacker
could exploit this vulnerability by performing SNMP polling on MIBs and
using only Interface Index (ifIndex) values. A successful exploit could
allow the attacker to increase CPU usage to 99% on an affected device and
cause a DoS condition.
There are workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-20170201-asrsnmp
Affected Products
Vulnerable Products
This vulnerability affects Cisco ASR 1000 Series Aggregation Services
Routers that are running Cisco IOS XE Software Release 3.13.6S, 3.16.2S, or
3.17.1S.
Determining the Cisco IOS XE Software Release
To determine which Cisco IOS XE Software release is running on a device,
administrators can log in to the device, use the show version command in
the CLI, and then refer to the system banner that appears. If the device is
running Cisco IOS XE Software, the system banner displays Cisco IOS XE
Software or similar text.
The following example shows the output of the show version command on a
device that is running Cisco IOS XE Software Release 3.17.01.S:
Router> show version
Cisco IOS XE Software, Version 03.17.01.S - Standard Support Release
Cisco IOS Software, ASR903 Software (PPC_LINUX_IOSD-UNIVERSALK9_NPE-M), Version 15.6(1)S1, RELEASE SOFTWARE (fc3)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Wed 09-Mar-16 06:34 by mcpre
.
.
.
For information about the naming and numbering conventions for Cisco IOS XE
Software releases, see White Paper: Cisco IOS and NX-OS Software Reference
Guide.
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this
vulnerability.
Indicators of Compromise
Exploitation of this vulnerability will cause high CPU usage by the SNMP
engine on an affected device. To assess CPU usage on a device,
administrators can use the show process cpu sorted command in the CLI. The
following example shows the output of the command for a device that has
high CPU usage by the SNMP engine, indicated in bold:
STLD1-630-03.03-ASR1000-RU38# show process cpu sorted
CPU utilization for five seconds: 100%/0%; one minute: 100%; five minutes: 100%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
54 1600083478 33340088 47993 99.97% 99.94% 99.95% 0 SNMP ENGINE
.
.
.
Exploitation of this vulnerability may also cause a
%SNMP-3-INPUT_QFULL_ERR: Packet dropped due to input queue full error to
occur.
Workarounds
If the device console is accessible, administrators can remove the SNMP
configuration to allow the CPU to recover and allow for a device upgrade to
a fixed release of the software.
If the device console is not accessible, administrators can power cycle the
device and either remove the SNMP configuration or prevent SNMP polling on
the device to allow for a device upgrade to a fixed release of the
software.
Fixed Software
For information about fixed software releases, consult the Cisco bug ID(s)
at the top of this advisory.
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.
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 discovered while responding to customer support
requests.
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.
URL
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170201-asrsnmp
Revision History
Version Description Section Status Date
1.0 Initial public release. Final 2017-February-01
Legal Disclaimer
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND
OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT
OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES
THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
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.
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.
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