Windows BSOD Error 0x00000020 — KERNEL_APC_PENDING_DURING_EXIT Fix

What Does This Error Mean?

The 0x00000020 blue screen means a thread tried to exit while it still had a pending kernel APC (Asynchronous Procedure Call) in the queue. This is called KERNEL_APC_PENDING_DURING_EXIT. It almost always points to a buggy kernel-mode driver that is not cleaning up properly before a thread ends.

Affected Models

Windows 10
Windows 11
Windows 8.1
Windows Server

Common Causes

A kernel-mode driver is not properly cancelling pending APC calls before thread exit
A corrupted or outdated driver is mishandling asynchronous operations
System files related to thread management are corrupted
A third-party storage or network driver is causing the APC queue to get stuck
Malware has infected a driver and disrupted normal APC handling

How to Fix It

Use WhoCrashed or WinDbg to identify the driver causing the error. Download WhoCrashed from resplendence.com, install it, and open it after the crash to see the culprit driver.

This step is worth doing first because it tells you exactly which driver to fix. Without this, you are guessing.
Update or roll back the identified driver. In Device Manager, right-click the device and choose 'Update driver' or 'Roll Back Driver' if a recent update caused the issue.

Rolling back is often the fastest fix if the problem started after a Windows Update.
Run System File Checker. Open Command Prompt as Administrator and type: sfc /scannow

This repairs corrupted kernel files that may be contributing to thread exit failures.
Run DISM to repair the Windows component store. Type: DISM /Online /Cleanup-Image /RestoreHealth in an elevated Command Prompt.

This downloads fresh system components from Windows Update and replaces any that are corrupted.
Scan for malware. Run a full system scan with Windows Defender or Malwarebytes to check for any drivers that have been tampered with.

Some malware specifically targets driver-level operations to maintain persistence on a system.

When to Call a Professional

If updating and reinstalling drivers does not fix this error, the issue may be in a driver that requires a vendor-issued patch. Contact the manufacturer of any recently updated hardware and report the crash. For business systems, IT support can use WinDbg to pinpoint the exact driver.

Frequently Asked Questions

What is a kernel APC?

An APC (Asynchronous Procedure Call) is a request queued for a thread to run when it has free time. Think of it like a sticky note left on someone's desk while they are busy. When the thread exits without reading its sticky notes, Windows detects the mistake and crashes.

Why does this happen after a Windows Update?

Windows Updates sometimes include driver updates that introduce new bugs. If the crash started right after a major Windows Update, rolling back the relevant driver is the first thing to try. You can check recent driver changes in Device Manager.

Does this error mean my computer is about to fail?

Not necessarily. This error is almost always software or driver related, not a sign of dying hardware. Most people fix it by updating or rolling back a driver. If the crash happens constantly, address it quickly to avoid any risk of file corruption.