A vulnerability in the implementation of an internal file management service for Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode that are running Cisco NX-OS Software could allow an unauthenticated, remote attacker to create, delete, or overwrite arbitrary files with root privileges on the device.
This vulnerability exists because TCP port 9075 is incorrectly configured to listen and respond to external connection requests. An attacker could exploit this vulnerability by sending crafted TCP packets to an IP address that is configured on a local interface on TCP port 9075. A successful exploit could allow the attacker to create, delete, or overwrite arbitrary files, including sensitive files that are related to the device configuration. For example, the attacker could add a user account without the device administrator knowing.
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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-3000-9000-fileaction-QtLzDRy2
This advisory is part of the February 2021 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: February 2021 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.
These devices are vulnerable by default.
To check a device, use the show sockets connection | include 9075 CLI command. If the command returns output, as shown in the following example, the device is vulnerable:
nexus# show sockets connection | include 9075
tcp LISTEN 0 32 * : 9075
Using infrastructure access control lists (iACLs) to allow only strictly required management and control plane traffic that is destined to the affected device, as recommended in the Cisco Guide to Securing NX-OS Software Devices, would prevent remote exploitation of this vulnerability. Customers are advised to explicitly deny all TCP packets that are destined to a locally configured IP address with a destination port of 9075 as part of their iACLs. A customized control plane policing (CoPP) policy may also be used to drop all TCP port 9075 traffic that is destined to an affected device.
Customers are advised to first evaluate the impact of configuration changes to the device and their security policy. Customers who are concerned about undesired or unexpected side effects are advised to contact their support organization before implementing configuration changes.
In addition, local exploitation of this vulnerability is possible if the NX-OS features bash or guestshell are enabled. There is no workaround or mitigation for a local attacker with valid device credentials; however, customers are advised to follow best practices for account management as outlined in the Cisco Guide to Securing NX-OS Software Devices - Use Authentication, Authorization, and Accounting.
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: end user license agreement
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 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.
Read more on the Cisco website.