Cisco Nexus Vulnerability Let Attackers Inject Malicious Commands

Cisco Systems has issued a critical security advisory addressing a command injection vulnerability in its Nexus 3000 and 9000 Series Switches operating in standalone NX-OS mode. 

Designated as CVE-2025-20161, the flaw allows authenticated local attackers with administrative privileges to execute arbitrary commands on the underlying operating system with root-level access. 

The vulnerability, discovered during internal testing by Cisco’s Advanced Security Initiatives Group (ASIG), underscores risks associated with software image validation in enterprise networking hardware.

Cisco Nexus Command Injection Vulnerability

CVE-2025-20161 stems from improper input validation during the software upgrade process.

Specifically, the switches fail to sanitize elements within a software image, enabling attackers to craft malicious images that inject commands into the operating system. 

The vulnerability leverages CWE-78 (OS Command Injection), a common weakness where untrusted data is passed to system commands. Exploitation requires valid administrator credentials, limiting immediate attack vectors to insider threats or compromised accounts.

The Common Vulnerability Scoring System (CVSS) assigns a base score of 5.1 (Medium severity). Command injection flaws in critical devices like switches, which often form the backbone of data centers, can lead to lateral movement, data exfiltration, or service disruption. 

Administrative credential requirements narrow the attack surface but raise concerns about insider threats and credential management practices.

Organizations reliant on Nexus switches should prioritize inventory audits to identify vulnerable devices and monitor logs for unauthorized upgrade attempts.

The vulnerability impacts all Cisco Nexus 3000 and 9000 Series Switches running standalone NX-OS software, regardless of configuration. 

Notably, devices operating in Application Centric Infrastructure (ACI) mode or other Cisco product lines, including Firepower and UCS Series, are unaffected.

Cisco has released patched software versions to remediate the flaw and urges administrators to upgrade immediately using the Cisco Software Checker tool. 

No workarounds exist, emphasizing the need for prompt action. 

The company also recommends verifying software image integrity via cryptographic hashes before installation, a practice that could mitigate risks from tampered files.

Mitigations

While CVE-2025-20161 has not been observed in active exploitation, its potential impact warrants urgent attention. Network administrators should:

• Apply Cisco’s security updates via the official Software Checker portal.
• Enforce strict access controls for administrative accounts.
• Implement hash verification for all software images.

Cisco’s proactive disclosure, coupled with the lack of viable workarounds, underscores the importance of maintaining rigorous patch management cycles. 

As enterprises increasingly rely on interconnected infrastructure, vulnerabilities in foundational networking components demand swift, systematic responses to safeguard operational integrity.

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