Handle null execution context in threadpool callback (#5605)

Fixes #5603

1 files changed, 6 insertions, 0 deletions

diff --git a/src/System.Private.CoreLib/src/System/Threading/Win32ThreadPoolNativeOverlapped.cs b/src/System.Private.CoreLib/src/System/Threading/Win32ThreadPoolNativeOverlapped.cs
index eb5debcf1..b7b2932cf 100644
--- a/src/System.Private.CoreLib/src/System/Threading/Win32ThreadPoolNativeOverlapped.cs
+++ b/src/System.Private.CoreLib/src/System/Threading/Win32ThreadPoolNativeOverlapped.cs
@@ -191,6 +191,12 @@ namespace System.Threading
             Debug.Assert(!data._completed);
             data._completed = true;
 
+            if (data._executionContext == null)
+            {
+                data._callback(errorCode, bytesWritten, ToNativeOverlapped(overlapped));
+                return;
+            }
+
             ContextCallback callback = s_executionContextCallback;
             if (callback == null)
                 s_executionContextCallback = callback = OnExecutionContextCallback;