CVE-2025-20161: Cisco Nexus Switches RCE Vulnerability

CVE-2025-20161 Overview

CVE-2025-20161 is a command injection vulnerability in the software upgrade process of Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches running in standalone NX-OS mode. The flaw stems from insufficient validation of specific elements within a software image. An authenticated local attacker with valid Administrator credentials can exploit the vulnerability by installing a crafted software image. Successful exploitation allows arbitrary command execution on the underlying operating system with root privileges. Cisco advises administrators to validate the hash of any software image before installation. The vulnerability is tracked under CWE-78: OS Command Injection.

Critical Impact
Attackers with Administrator credentials can escape the NX-OS management shell and execute arbitrary commands as root on affected Nexus switches by installing a crafted image.

Affected Products

Cisco Nexus 3000 Series Switches (standalone NX-OS mode)
Cisco Nexus 9000 Series Switches (standalone NX-OS mode)
Devices running vulnerable Cisco NX-OS Software releases

Discovery Timeline

2025-02-26 - CVE-2025-20161 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-20161

Vulnerability Analysis

The vulnerability resides in the NX-OS software upgrade workflow. During image installation, the upgrade process parses metadata and elements embedded within the software image file. Insufficient validation of these elements allows attacker-controlled data to be interpreted as shell commands by the underlying Linux operating system. Because the upgrade process executes with root privileges, injected commands run outside the restricted NX-OS CLI boundary. This provides a privilege boundary bypass: the Administrator role on NX-OS is intentionally restricted from direct root shell access, but the upgrade path breaks that security model.

Root Cause

The root cause is improper neutralization of special elements used in an operating system command [CWE-78]. The image installer trusts fields within the software image without sufficient sanitization. When those fields are passed to underlying OS commands during unpacking or verification, injected shell metacharacters alter the intended command and execute attacker-supplied payloads.

Attack Vector

Exploitation requires local access to the device with valid Administrator credentials. The attacker crafts a malicious NX-OS image containing injected content within the parsed elements, transfers the image to the switch, and initiates the upgrade with standard installation commands. The injected commands execute as root on the host operating system. The attack vector is local and privileges required are high, which limits exploitation to compromised administrator sessions or malicious insiders. No user interaction is required beyond the attacker-initiated install.

No public proof-of-concept is available. See the Cisco Security Advisory for technical details.

Detection Methods for CVE-2025-20161

Indicators of Compromise

Installation of NX-OS images whose SHA-512 hashes do not match values published by Cisco on the official software download portal.
Unexpected install or boot command activity in device accounting logs that correlates with image transfers from untrusted sources.
Appearance of unauthorized processes, cron entries, or files on the device filesystem following an upgrade event.

Detection Strategies

Compare the hash of every image staged on the device against Cisco-published hashes before executing install all or equivalent upgrade commands.
Centralize NX-OS syslog and TACACS+/AAA command accounting to a SIEM and alert on install, copy, and boot variable commands executed outside approved change windows.
Monitor administrative sessions for anomalous image uploads via scp, tftp, or ftp to the bootflash: filesystem.

Monitoring Recommendations

Ingest Cisco NX-OS logs and AAA command accounting into a centralized analytics platform for correlation with change management records.
Alert on administrative logins from unusual source addresses or outside maintenance windows, since exploitation requires valid Administrator credentials.
Track configuration and image inventory drift using Cisco DNA Center, NDFC, or equivalent network management tooling.

How to Mitigate CVE-2025-20161

Immediate Actions Required

Apply the fixed NX-OS release identified in the Cisco Security Advisory cisco-sa-nxos-ici-dpOjbWxk for Nexus 3000 and Nexus 9000 switches in standalone NX-OS mode.
Validate the SHA-512 hash of every NX-OS image against Cisco-published values before executing any upgrade.
Restrict Administrator role assignment and enforce multi-factor authentication for all privileged NX-OS accounts.
Review AAA command accounting for recent install activity and investigate any image installations that cannot be tied to approved change tickets.

Patch Information

Cisco has released fixed software addressing CVE-2025-20161. Refer to the Cisco Security Advisory cisco-sa-nxos-ici-dpOjbWxk for the complete list of fixed releases per platform and upgrade guidance. There are no listed workarounds that fully remove the vulnerability other than upgrading to a fixed release.

Workarounds

Download NX-OS images only from the official Cisco Software Download portal over trusted channels.
Verify image integrity using show file bootflash:<image> sha512sum and compare against the hash published by Cisco before any install all operation.
Limit bootflash: write access to approved administrators and restrict file transfer protocols on the management plane.
Enforce strict change control so that image installations occur only during approved windows with dual authorization.