This happens only on 3.4.3. (Reverting back to 3.4.2 solved the issue, so should be just a regression)
The stack trace is:
[AsyncContextImpl] onError() call failed for listener of type [org.apache.catalina.core.AsyncListenerWrapper]
java.lang.NullPointerException: Cannot invoke "java.lang.Throwable.getMessage()" because the return value of "org.springframework.core.NestedExceptionUtils.getMostSpecificCause(java.lang.Throwable)" is null
at org.springframework.web.util.DisconnectedClientHelper.isClientDisconnectedException(DisconnectedClientHelper.java:120)
at org.springframework.web.context.request.async.WebAsyncManager.lambda$startDeferredResultProcessing$6(WebAsyncManager.java:450)
at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.lambda$onError$0(StandardServletAsyncWebRequest.java:195)
Comment From: nosan
Duplicate of https://github.com/spring-projects/spring-framework/issues/34533