CVE-2022-20650: Cisco NX-OS NX-API RCE Vulnerability

CVE-2022-20650 Overview

A command injection vulnerability exists in the NX-API feature of Cisco NX-OS Software that could allow an authenticated, remote attacker to execute arbitrary commands with root privileges on the underlying operating system. The vulnerability stems from insufficient input validation of user-supplied data sent to the NX-API, enabling attackers to inject malicious commands through crafted HTTP POST requests.

Critical Impact

Successful exploitation grants attackers root-level command execution on affected Cisco Nexus switches, potentially leading to complete device compromise, network infrastructure takeover, and lateral movement within enterprise networks.

Affected Products

• Cisco NX-OS Software (versions 7.3(8)N1(0.4) and 10.2(1.72) confirmed)
• Cisco Nexus 3000 Series Switches (3048, 31108PC-V, 31108TC-V, 3132C-Z, 3232C, 3264C-E, 3408-S, 3432D-S, 3464C, and others)
• Cisco Nexus 5000 Series Switches (5548P, 5548UP, 5596T, 5596UP, 56128P, 5672UP)
• Cisco Nexus 6000 Series Switches (6000, 6001, 6004)
• Cisco Nexus 9000 Series Switches (9236C, 9272Q, 9332C, 9336C-FX2, 9364C, 9504, 9508, 9516, and numerous others)

Discovery Timeline

• February 23, 2022 - CVE-2022-20650 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-20650

Vulnerability Analysis

This vulnerability (CWE-78: OS Command Injection) affects the NX-API feature in Cisco NX-OS Software. The NX-API provides a programmatic interface for managing Nexus switches via HTTP/HTTPS, allowing administrators to execute CLI commands and retrieve device configuration through RESTful API calls. The vulnerability exists because the NX-API fails to properly sanitize user-supplied input before passing it to system shell commands.

When an authenticated attacker sends specially crafted input through HTTP POST requests to the NX-API endpoint, the malicious payload bypasses input validation controls and is executed directly by the underlying Linux operating system with root privileges. This allows complete compromise of the affected device.

It is important to note that the NX-API feature is disabled by default on Cisco NX-OS devices. However, organizations that have enabled this feature for automation, orchestration, or management purposes are at risk. The vulnerability requires valid authentication credentials, meaning an attacker must first obtain legitimate access to the NX-API before exploitation.

Root Cause

The root cause of CVE-2022-20650 is insufficient input validation within the NX-API request processing logic. User-supplied data received through the API is not adequately sanitized before being incorporated into operating system commands. This allows specially crafted input containing shell metacharacters or command separators to break out of the intended command context and execute arbitrary commands.

The NX-API processes incoming HTTP POST requests and extracts parameters that are subsequently used in system-level operations. Without proper escaping or validation of these parameters, an attacker can inject additional commands that execute with the same privileges as the NX-API process—which runs as root on Cisco NX-OS.

Attack Vector

The attack is network-based and targets the NX-API HTTP/HTTPS interface. An attacker with valid credentials to access the NX-API can construct malicious HTTP POST requests containing command injection payloads. The attack flow involves:

1. The attacker authenticates to the NX-API using valid credentials (obtained through phishing, credential theft, or insider access)
2. A crafted HTTP POST request is sent to the NX-API endpoint containing shell command injection payloads embedded within API parameters
3. The vulnerable NX-API processing code fails to sanitize the malicious input
4. The injected commands are executed by the underlying operating system with root privileges
5. The attacker gains full control over the affected Nexus switch

Since NX-API typically operates over HTTPS on port 443 (or HTTP on port 80), the attack traffic may appear as legitimate management traffic, making detection more challenging without deep packet inspection or behavioral analysis.

Detection Methods for CVE-2022-20650

Indicators of Compromise

• Unusual HTTP POST requests to NX-API endpoints containing shell metacharacters (;, |, &&, backticks, $()) in API parameters
• Unexpected root-level processes spawned on Nexus switches, particularly from NX-API handler processes
• Anomalous command execution patterns in NX-OS system logs, especially commands not typically used in normal operations
• New or modified user accounts, SSH keys, or configuration changes made outside of change management windows
• Network connections from Nexus switches to external or unauthorized IP addresses

Detection Strategies

• Implement network-based IDS/IPS rules to detect command injection patterns in HTTP/HTTPS traffic destined for NX-API endpoints
• Enable comprehensive logging on NX-API access and monitor for anomalous request patterns or failed authentication attempts followed by successful ones
• Deploy behavioral analytics to establish baseline NX-API usage and alert on deviations such as unusual command structures or request volumes
• Configure SIEM correlation rules to detect sequences of authentication events followed by suspicious API activity on Nexus infrastructure

Monitoring Recommendations

• Enable and centralize NX-OS accounting logs to capture all CLI and NX-API command execution with timestamps and source information
• Monitor process execution on Nexus switches for unexpected child processes spawned by NX-API components
• Implement netflow or traffic analysis for management plane traffic to detect unusual patterns or data exfiltration attempts
• Regularly audit NX-API access logs for requests containing special characters or unusually long parameter values

How to Mitigate CVE-2022-20650

Immediate Actions Required

• Verify NX-API feature status on all Cisco Nexus switches and disable it on devices where it is not operationally required using the command no feature nxapi
• Apply Cisco security patches immediately on all affected devices running vulnerable NX-OS versions
• Implement strict access control lists (ACLs) to limit NX-API access to authorized management networks and IP addresses only
• Rotate credentials for all accounts with NX-API access and enforce strong password policies
• Enable multi-factor authentication for NX-API access where supported

Patch Information

Cisco has released security updates addressing CVE-2022-20650. Organizations should consult the Cisco Security Advisory for specific fixed software versions applicable to their hardware platforms. The advisory provides detailed information on affected and fixed releases for each Nexus platform series.

Administrators should prioritize patching based on network criticality and exposure. Devices with NX-API enabled and accessible from less-trusted network segments should be prioritized for immediate remediation.

Workarounds

• Disable the NX-API feature entirely if it is not required for operations: configure terminal followed by no feature nxapi
• Implement management plane ACLs to restrict NX-API access to only trusted management stations and jump hosts
• Use out-of-band management networks isolated from production traffic to reduce attack surface exposure
• Enable HTTPS only for NX-API (disable HTTP) and ensure valid certificates are configured to prevent credential interception

# Disable NX-API feature if not required
configure terminal
no feature nxapi

# If NX-API is required, restrict access with ACL
ip access-list NXAPI-MGMT-ACL
  permit tcp 10.0.0.0/8 any eq 443
  deny ip any any log

# Apply ACL to NX-API
nxapi http
  access-class NXAPI-MGMT-ACL