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
-
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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170201-asrsnmp
-
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 . . .
Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this vulnerability.
-
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 . . .
-
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.
-
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.
-
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.
-
This vulnerability was discovered while responding to customer support requests.
-
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.
-
Version Description Section Status Date 1.0 Initial public release. — Final 2017-February-01
-
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.