Fix RPC_NT_SS_HANDLES_MISMATCH (0XC0030007) Error

Quick answer: Restart the RPC service and the application that triggered the error. If that doesn't work, check the DCOM settings for the specific component involved — you'll likely find a misconfigured interface or a stale handle.

What's going on here?

This error — RPC_NT_SS_HANDLES_MISMATCH (0XC0030007) — tells you the RPC runtime is confused. The client and server passed different binding handles to each other. Think of a binding handle like a phone number: if you give someone one number and they call you back on a different one, the conversation breaks. That's exactly what's happening here.

I've seen this mostly in two places: old DCOM apps that haven't been updated since Windows 7, and custom in-house apps that weren't tested across network boundaries. It shows up when one side of the RPC connection uses a handle from one session, and the other side uses a handle from another session — or from no session at all.

Here's the real-world trigger: you're running a legacy accounting app on a Windows Server 2019 box. The client connects fine for an hour, then suddenly throws this error when you try to save a report. The app's RPC endpoint probably dropped the original handle and tried to reuse a cached one that expired.

Step-by-step fix

Restart the application. Close the client and server apps completely. Wait 10 seconds. Open them again. This clears any stale handles in memory. Most people stop here — and it works about 30% of the time.
Restart the RPC service. Press Win + R, type services.msc, and hit Enter. Find Remote Procedure Call (RPC) in the list. Right-click it and select Restart. This resets all RPC endpoints on the machine. Expect the app to disconnect and reconnect — that's normal.
Check DCOM configuration. Open Component Services (type dcomcnfg in Run). Navigate to Component Services > Computers > My Computer > DCOM Config. Find your application's component (you'll need the AppID from the event log). Right-click it, go to Properties, and on the Endpoints tab, make sure the dynamic endpoint range is enabled. Also check the Security tab — the user running the app needs Launch and Activation permissions.
Verify the binding order. If your app uses a specific protocol sequence (like ncacn_ip_tcp), make sure the client and server both agree on it. Mismatches in protocol sequence cause this error. Check the app's configuration file for lines like Endpoint= or Protocol=.
Clear the RPC port range. Sometimes ports get reserved. Run this in an elevated Command Prompt: netsh rpc reset. Then restart the RPC service. This flushes the port allocation table.

Alternative fixes if the main steps don't work

Reinstall the application. This is nuclear option, but it often works if the app's RPC registration got corrupted. Uninstall, reboot, reinstall.
Update your network drivers. I've seen a Realtek NIC driver from 2016 cause handle mismatches because it didn't properly handle RPC callbacks. Download the latest driver from the manufacturer's site.
Disable IPv6 if you're on IPv4-only. In the network adapter properties, uncheck Internet Protocol Version 6 (TCP/IPv6). Some RPC implementations get confused by dual-stack environments.
Add a static RPC port. For stable DCOM apps, set a fixed port range in the registry at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Rpc\Internet. Create a Ports REG_MULTI_SZ value with a range like 5000-5020. Reboot.

Prevention tip

Check your app's RPC timeout settings. If the client and server are idle for too long, the handles get recycled by the OS. Increase the idle timeout in the app's configuration to match your usage pattern. Also — and this is the one everyone forgets — make sure the system clocks on the client and server are synced to within 5 seconds. NTP drift kills RPC handles faster than anything else.