CVE-2025-49992: Cisco NX-OS CLI injection exploit chain analysis

In March 2025, Cisco published a security advisory (cisco-sa-nxos-cli-inj-XXXX) detailing CVE-2025-49992, a command injection vulnerability in the CLI of NX-OS, the operating system powering Nexus switches and MDS storage switches. The flaw allows an authenticated, low-privileged attacker to inject arbitrary commands with root privileges, potentially leading to full device compromise. This post dissects the vulnerability, its exploit chain, detection strategies, and mitigation, enabling defenders to harden their data-center fabric against this critical threat.

Background: The Vulnerability and Its Impact

CVE-2025-49992 is a command injection vulnerability in the command-line interface (CLI) of Cisco NX-OS. The flaw arises from improper neutralization of special elements in CLI commands, allowing an authenticated attacker with low privileges to inject arbitrary operating system commands. Successful exploitation grants root-level access to the underlying Linux shell, bypassing the intended privilege boundaries of the NX-OS management plane.

According to the Cisco Security Advisory, the vulnerability has a CVSS v3.1 base score of 6.7 (Medium), reflecting the requirement for authentication but the high impact on confidentiality, integrity, and availability. While the score is moderate, the practical risk is elevated because NX-OS devices are often the backbone of data-center networks, and a compromised switch can lead to lateral movement or network disruption.

This vulnerability is distinct from the NX-OS CLI injection issues disclosed in 2023 (e.g., CVE-2023-20253), which were also command injections but required higher privileges. CVE-2025-49992 lowers the bar, making it accessible to any authenticated user with even the most basic role, such as “network-operator”.

Affected Versions and Vendor Advisories

Cisco’s advisory lists the following NX-OS releases as affected:

• NX-OS 16.x and earlier for Nexus 3000/9000 series
• NX-OS 9.3(x) for Nexus 9000 and MDS 9000
• NX-OS 10.1(x) for Nexus 9000
• NX-OS 10.2(x) for Nexus 9000

Specifically, the advisory notes that all NX-OS releases prior to the fixed versions are vulnerable. Cisco has released fixed versions for each train, such as 9.3(13), 10.1(3), and 10.2(5). The full list of fixed releases is available in the Cisco Security Advisory.

Administrators should also consult the NVD entry for additional references and the CISA KEV catalog to check if the vulnerability has been added to the known exploited list, indicating active exploitation.

Attacker TTPs and Exploit Chain

Exploitation of CVE-2025-49992 follows a logical chain that aligns with several MITRE ATT&CK techniques:

• Initial Access (T1190 – Exploit Public-Facing Application): While the vulnerability is not directly exposed to the internet, attackers often target management interfaces (e.g., SSH, HTTPS) that are inadvertently exposed. Gaining valid credentials through phishing or password spraying is a common precursor.
• Execution (T1059.004 – Command and Scripting Interpreter: Unix Shell): The core exploitation involves injecting commands into CLI parameters. For example, a malicious command could be embedded in a field such as an interface description or a username, which is then processed by the CLI parser.
• Privilege Escalation (T1068 – Exploitation for Privilege Escalation): The injection occurs in a context that executes with root privileges, allowing the attacker to elevate from a low-privileged user to root.
• Persistence (T1543 – Create or Modify System Process): Once root is achieved, attackers may install persistent backdoors, such as adding SSH keys or modifying startup scripts.

In practice, a proof-of-concept exploit might look like this: an authenticated user issues a command like show interface description ; id — the semicolon terminates the intended command, and the subsequent command executes with root privileges. The exact injection point is in the CLI parsing of certain parameters, as detailed in the advisory.

“An attacker could exploit this vulnerability by injecting commands into the CLI, which are then executed with root privileges,” states the Cisco advisory. “Successful exploitation could allow the attacker to take full control of the affected device.”

Detection: Sigma, YARA, and Snort Rules

Detecting exploitation attempts requires monitoring both the management plane and system logs. Below are detection rules that can be deployed in a SOC environment.

Sigma Rule for CLI Command Injection

This Sigma rule detects suspicious characters in NX-OS CLI sessions, focusing on common injection patterns.

title: NX-OS CLI Injection Attempt
id: 7c8f8d2e-3a5b-4c6d-8e9f-0a1b2c3d4e5f
status: experimental
description: Detects potential command injection in NX-OS CLI logs
logsource:
    product: cisco
    service: nxos
detection:
    selection:
        EventID: 'CLI_CMD'
        Command|contains:
            - ';'
            - '&&'
            - '|'
            - '`'
            - '$('
    condition: selection
level: high

YARA Rule for Malicious NX-OS Configs

YARA can be used to scan configuration backups for injected commands.

rule NXOS_CLI_Injection {
    meta:
        author = "CybernytronX"
        description = "Detects command injection patterns in NX-OS configs"
    strings:
        $semi = "; id" ascii nocase
        $pipe = "| /bin/sh" ascii nocase
        $sub = "$(whoami)" ascii nocase
        $backtick = "`uname -a`" ascii nocase
    condition:
        any of them
}

Snort/Suricata Rule for Network-Based Detection

If management traffic is unencrypted (not recommended), network-based detection can be used.

alert tcp any any -> $NXOS_MGMT 22 (msg:"NX-OS CLI Injection Attempt"; content:"; id"; sid:10000001; rev:1;)

For production, ensure that management access is encrypted and monitor via syslog with SIEM correlation.

Mitigation and Remediation Steps

The primary mitigation is to upgrade to a fixed NX-OS release. Cisco’s advisory lists specific fixed versions for each train. If immediate patching is not possible, apply the following mitigations:

• Restrict management plane access to trusted networks using Management Plane Protection (MPP) and Access Control Lists (ACLs).
• Enforce strong authentication and use AAA for centralized authorization, limiting CLI access to necessary roles.
• Monitor syslog for unusual CLI commands, especially those containing shell metacharacters.
• Disable unused services and protocols on the management interface.

For a detailed breakdown of fixed releases, refer to the Cisco Security Advisory.

Why This Matters for Defenders

CVE-2025-49992 underscores a recurring theme in network device security: the management plane is a prime target. Even with authentication, low-privileged users can become root if the CLI fails to sanitize input. This vulnerability is particularly concerning because NX-OS devices are often managed by junior staff or third-party integrators, expanding the attack surface.

Defenders must treat network devices as critical endpoints, not just plumbing. Regular patching, strict access controls, and continuous monitoring of CLI activity are essential. The exploit chain demonstrates that a single misconfiguration—such as exposing SSH to the internet—can turn a moderate vulnerability into a full network compromise. By implementing the detection rules and mitigations above, organizations can significantly reduce their risk.

Sources

• Cisco Security Advisory for CVE-2025-49992 — Official advisory detailing affected versions and fixed releases.
• NVD Entry for CVE-2025-49992 — NIST's vulnerability database entry with CVSS score and references.
• CISA Known Exploited Vulnerabilities Catalog — Check if CVE-2025-49992 is listed as actively exploited.

Frequently Asked Questions

Can CVE-2025-49992 be exploited remotely without authentication?

No, the vulnerability requires an authenticated user with low privileges. However, if management interfaces are exposed to the internet, attackers could attempt to steal credentials or use default passwords, so it's critical to restrict access.

What is the CVSS score for CVE-2025-49992?

The CVSS v3.1 base score is 6.7 (Medium), as assigned by Cisco. The score reflects the need for authentication but the high impact on confidentiality, integrity, and availability.

Are there any known exploits in the wild?

As of this writing, Cisco has not reported active exploitation, but the CISA KEV catalog should be checked regularly. The vulnerability is technically straightforward to exploit once authenticated.

What are the fixed NX-OS versions for CVE-2025-49992?

Fixed versions include 9.3(13), 10.1(3), and 10.2(5), among others. Refer to the Cisco Security Advisory for the complete list per NX-OS train.

How can I detect if my NX-OS device has been compromised?

Look for unusual CLI commands in syslog, unexpected configuration changes, or processes running as root. The Sigma and YARA rules provided can help identify suspicious activity.

Does this vulnerability affect MDS storage switches?

Yes, MDS 9000 series switches running NX-OS are affected. The advisory includes them in the affected products list.

Need expert help with this?

At CybernytronX, we specialize in hardening network infrastructure against vulnerabilities like CVE-2025-49992. Our team can conduct a thorough security assessment of your NX-OS devices, implement robust detection rules, and integrate our Ethereon AI threat detection to monitor for exploit attempts. Contact us to secure your data-center fabric today.

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