A vulnerability in a specific CLI command that is run on Cisco IOS XE SD-WAN Software could allow an authenticated, local attacker to overwrite arbitrary files in the configuration database of an affected device.
This vulnerability is due to insufficient validation of specific CLI command parameters. An attacker could exploit this vulnerability by issuing that command with specific parameters. A successful exploit could allow the attacker to overwrite the content of the configuration database and gain root-level access to an affected device.
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:
This advisory is part of the September 2021 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2021 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication.
At the time of publication, this vulnerability affected the following Cisco products if they were running a vulnerable release of Cisco IOS XE SD-WAN Software and had the SD-WAN feature enabled:
- 1000 Series Integrated Services Routers (ISRs)
- 4000 Series ISRs
- ASR 1000 Series Aggregation Services Routers (ASRs)
- Cloud Services Router (CSR) 1000V Series
Note: The SD-WAN feature is not enabled by default.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine the Device Configuration
There are two methods for determining whether the SD-WAN feature is enabled on a device:
Option 1: Use the show running-config | include sdwan Command
To determine whether sdwan mode is enabled on a device, use the show running-config | include sdwan command and check the tunnel mode in the output. If the command returns tunnel mode sdwan, the sdwan feature is enabled and the device is vulnerable. If the command returns no output or the command does not exist, the SD-WAN feature is not enabled and the device is not affected by this vulnerability.
The following example shows the output of the show running-config | include sdwan command on a device that has the SD-WAN feature enabled:
Router# show running-config | include sdwan
tunnel mode sdwan
Option 2: Use the show version Command
Alternatively, use the show version command to determine whether the Cisco IOS XE device is in Controller mode. The end of the output includes the router operating mode, which indicates whether the device is in Controller mode.
The following example shows part of the show version command output on a device that has the SD-WAN feature enabled:
Router# show version
Router operating mode: Controller-Managed
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:
- IOS Software
- IOS XR Software
- Meraki products
- NX-OS Software
There are no workarounds that address this vulnerability.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories 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.
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 found during internal security testing by James Spadaro of the Cisco Advanced Security Initiatives Group (ASIG).
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 2021-SEP-22
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