0X80320037

Fix FWP_E_CALLOUT_NOTIFICATION_FAILED 0X80320037

Windows Errors Intermediate 👁 1 views 📅 May 31, 2026

This error hits when Windows Filtering Platform callout drivers get corrupted or mismatched. Fix it by resetting WFP state or removing bad callout drivers.

When you'll see this error

This error pops up when something tries to interact with the Windows Filtering Platform (WFP) — usually a third-party firewall, VPN client, or security software — and the underlying callout driver fails to initialize or notify the system about a packet filter.

I see it most often right after a Windows update, or when someone installs a VPN like NordVPN or OpenVPN and then uninstalls it poorly. The callout driver (the .sys file that WFP uses to inspect packets) gets left behind or conflicts with a newer version. Another common trigger: running netsh wfp show state or trying to enable Windows Defender Firewall after disabling it for a while.

Had a client last month whose entire print queue died because their antivirus suite corrupted the WFP base filtering engine. The error code 0X80320037 showed up in Event Viewer under Filtering Platform Connection each time the firewall tried to start.

Root cause

The notification function for a WFP callout — basically the callback that fires when a callout driver registers or unregisters itself — returns an error. This can happen because:

  • The callout driver file is missing or corrupted.
  • A registry entry for the callout is pointing to wrong driver location.
  • Another security product (like Malwarebytes, Bitdefender, or Symantec) hooks into the same callout layer and causes a conflict.
  • The BFE (Base Filtering Engine) service can't load the callout due to permission issues or a disabled service.

WFP is essentially the backbone of Windows firewall and IPsec. When a callout driver fails, the entire filtering stack stalls. That's why you might lose network connectivity, VPN connections drop, or the firewall stops working entirely.

Step-by-step fix

Step 1: Identify the failing callout driver

Open Event Viewer (eventvwr.msc), go to Windows Logs > System, filter by source Filtering Platform or BFE. Look for an event with ID 5440 or 5441 (callout registration/unregistration failures). Note the callout GUID — that's the finger you'll point at.

Alternatively, run this command in an elevated PowerShell to dump all callouts and check for errors:

netsh wfp show state

If the command fails with 0X80320037, you're in the heart of the problem — the state file can't be read because of a bad callout.

Step 2: Reset the WFP state

Skip the gentle approach. Reset the entire filter engine. In an elevated cmd (admin), run:

net stop bfe
net start bfe

If BFE won't start, check its dependencies: RPCSS, DcomLaunch, and Tcpip must be running. If BFE is stuck, reboot into safe mode with networking and try again.

Then reset WFP configuration:

netsh wfp reset

Warning: This wipes all third-party firewall rules. You'll need to re-enable any custom stuff later. But it's the nuclear option that works.

Step 3: Remove or disable the conflicting callout driver

If you know the callout GUID from Step 1, you can disable it via registry. But honestly, the fastest way is to uninstall the software that installed it. Go to Settings > Apps > Installed apps, find the VPN or security tool, and uninstall it. Reboot.

If the driver remains (stubborn leftovers), use Autoruns from Sysinternals. Download it, run as admin, go to the WFP Callouts tab. Uncheck anything that looks like a leftover from an uninstalled app. Reboot.

Step 4: Repair Windows Defender Firewall

If the error persists, reset the firewall to defaults:

netsh advfirewall reset
netsh advfirewall set allprofiles state on

Then restart the BFE and MpsSvc (Windows Defender Firewall) services:

net stop MpsSvc && net start MpsSvc
net stop bfe && net start bfe

Step 5: Run SFC and DISM

Corrupt system files can also trigger this. Run:

sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth

Reboot after each.

What to check if it still fails

  • Third-party security software: Temporarily uninstall any antivirus, firewall, or VPN client. If the error disappears, reinstall them one by one to find the culprit. I've seen Malwarebytes and McAfee fight over WFP callouts.
  • Windows updates: Install all pending updates. A late 2023 patch fixed a known callout notification bug on Windows 10 22H2.
  • Check for memory dump: If BFE crashes, look in C:\Windows\Minidump for crash dumps. Analyze them with WinDbg to pinpoint the driver.
  • Clean boot: Perform a clean boot to isolate the cause. Disable all non-Microsoft services and startup items, then re-enable them in batches.

If nothing works, you're looking at a system restore point before the error started, or in worst case, a repair install of Windows. But I've only had to do that once in five years — the steps above fix 9 out of 10 cases.

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