Cisco has released a critical advisory for a command injection vulnerability (CVE-2025-20161) affecting its Nexus 3000 and 9000 Series switches running in standalone NX-OS mode.
Cisco Nexus Vulnerability
This flaw allows authenticated local attackers with administrative privileges to execute arbitrary commands on the underlying operating system with root-level access.
The vulnerability was discovered by Cisco’s Advanced Security Initiatives Group (ASIG) during internal testing, highlighting the security risks tied to software image validation in enterprise network devices.
CVE-2025-20161 exists due to improper input validation during the software upgrade process in Cisco Nexus switches.
The devices fail to properly sanitize parts of the software image, allowing attackers to embed commands that run on the operating system.
This is a classic example of OS Command Injection (CWE-78), where untrusted input gets passed to system-level commands.
Exploiting this flaw requires valid administrator credentials, so the primary risks come from insider threats or compromised admin accounts.
The vulnerability has a CVSS score of 5.1 (Medium), but command injection in core infrastructure like data center switches could enable attackers to move laterally, steal data, or disrupt critical services.
The need for administrative credentials limits the attack surface but raises concerns about insider threats and credential management.
Organizations should audit Nexus switches and monitor logs for unauthorized upgrade attempts.
The vulnerability affects all Cisco Nexus 3000 and 9000 Series Switches running standalone NX-OS. Devices in ACI mode and other Cisco products are unaffected.
Cisco has released patches and urges immediate upgrades using the Cisco Software Checker tool.
No workarounds are available, so quick action is required.
Verifying software image integrity with cryptographic hashes before installation can help prevent risks from tampered files.
Mitigations
Although CVE-2025-20161 has not been actively exploited, its potential impact requires immediate action. Network administrators should:
- Apply Cisco’s security updates using the official Software Checker portal.
- Enforce strict access controls for administrative accounts.
- Implement hash verification for all software images.
Cisco’s proactive disclosure highlights the importance of maintaining rigorous patch management practices, especially since no workarounds exist.
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