Cisco Security Advisory
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CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
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A vulnerability in the Simple Network Management Protocol (SNMP) implementation in Cisco ASR 920 Series Aggregation Services Router model ASR920-12SZ-IM could allow an authenticated, remote attacker to cause the device to reload.
The vulnerability is due to incorrect handling of data that is returned for Cisco Discovery Protocol queries to SNMP. An attacker could exploit this vulnerability by sending a request for Cisco Discovery Protocol information by using SNMP. An exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition.
Cisco has released software updates that address this vulnerability. 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-asr920-ABjcLmef
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Vulnerable Products
This vulnerability affects the Cisco ASR 920 Series Aggregation Services Router model ASR920-12SZ-IM if it is configured with both SNMP (either Version 2c or 3) and Cisco Discovery Protocol.
For information about which Cisco IOS XE Software releases for Cisco ASR model ASR920-12SZ-IM are vulnerable, see the Fixed Software section of this advisory.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
No other models of the Cisco ASR 920 Series Aggregation Services Routers are affected by this vulnerability.
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This advisory has been scored as having a Medium Security Impact Rating (SIR) rather than a High SIR because the exploit does not consistently cause the device to be reloaded.
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Excluding the MIB CISCO-CDP-MIB is a workaround for this vulnerability. The following example shows exclusion of CISCO-CDP-MIB.
1. Create the cutdown view:
snmp-server view cutdown iso included snmp-server view cutdown 1.3.6.1.4.1.9.9.23 excluded
2. Apply the cutdown view to the SNMPv2 community string or SNMPv3 group:
#SNMPv2: snmp-server community Examplev2 view cutdown #SNMPv3: SNMP-Server group Examplev3Group v3 priv Read cutdown Write cutdown
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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.
Cisco IOS and IOS XE Software
To help customers determine their exposure to vulnerabilities in Cisco IOS and IOS XE Software, Cisco provides the Cisco Software Checker to identify any Cisco Security Advisories that impact a specific software release and the earliest release that fixes the vulnerabilities described in each advisory (“First Fixed”). If applicable, the tool also returns the earliest release that fixes all the vulnerabilities described in all the advisories identified (“Combined First Fixed”).
Customers can use the Cisco Software Checker to search advisories in the following ways:
- Choose the software and one or more releases
- Upload a .txt file that includes a list of specific releases
- Enter the output of the show version command
After initiating a search, customers can customize the search to include all Cisco Security Advisories, a specific advisory, or all advisories in the most recent bundled publication.
Customers can also use the following form to determine whether a release is affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE Software release—for example, 15.1(4)M2 or 3.13.8S:
By default, the Cisco Software Checker includes results only for vulnerabilities that have a Critical or High Security Impact Rating (SIR). To include results for Medium SIR vulnerabilities, customers can use the Cisco Software Checker on Cisco.com and check the Medium check box in the drop-down list under Impact Rating when customizing a search.
For a mapping of Cisco IOS XE Software releases to Cisco IOS Software releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the Cisco IOS XE Software release.
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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.
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This vulnerability was found during the resolution of a Cisco TAC support case.
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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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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2020-JUN-03
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