Concurrency Bug in Java 4.27+ Static Initialization leads to NPE #20599

What version of protobuf and what language are you using?
Version: 4.27+
Language: Java

What operating system (Linux, Windows, ...) and version?
Any OS

What did you do?
Initialized Generated Protobuf Messages in parallel.

Steps to reproduce the behavior:
https://github.com/nordnet/protobuf-issue/

What did you expect to see
No Error.

What did you see instead?
NPE + Stacktrace like the following:

java.lang.ExceptionInInitializerError
at com.google.devtools.cloudtrace.v2.Span.getDescriptor(Span.java:62)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.lang.NullPointerException: Cannot invoke "com.google.protobuf.DescriptorProtos$FeatureSet.getExtension(com.google.protobuf.ExtensionLite)" because the return value of "com.google.protobuf.Descriptors$FieldDescriptor.getFeatures()" is null
at com.google.protobuf.Descriptors$FieldDescriptor.legacyEnumFieldTreatedAsClosed(Descriptors.java:1582)
at com.google.protobuf.MessageReflection.mergeFieldFrom(MessageReflection.java:1219)
at com.google.protobuf.GeneratedMessage$ExtendableBuilder.parseUnknownField(GeneratedMessage.java:1630)
at com.google.protobuf.DescriptorProtos$FieldOptions$Builder.mergeFrom(DescriptorProtos.java:29650)
at com.google.protobuf.DescriptorProtos$FieldOptions$Builder.mergeFrom(DescriptorProtos.java:29179)
at com.google.protobuf.CodedInputStream$ArrayDecoder.readMessage(CodedInputStream.java:853)
at com.google.protobuf.DescriptorProtos$FieldDescriptorProto$Builder.mergeFrom(DescriptorProtos.java:13676)
at com.google.protobuf.DescriptorProtos$FieldDescriptorProto$1.parsePartialFrom(DescriptorProtos.java:14461)
at com.google.protobuf.DescriptorProtos$FieldDescriptorProto$1.parsePartialFrom(DescriptorProtos.java:14453)
at com.google.protobuf.CodedInputStream$ArrayDecoder.readMessage(CodedInputStream.java:869)
at com.google.protobuf.DescriptorProtos$DescriptorProto$Builder.mergeFrom(DescriptorProtos.java:7393)
at com.google.protobuf.DescriptorProtos$DescriptorProto$1.parsePartialFrom(DescriptorProtos.java:9525)
at com.google.protobuf.DescriptorProtos$DescriptorProto$1.parsePartialFrom(DescriptorProtos.java:9517)
at com.google.protobuf.CodedInputStream$ArrayDecoder.readMessage(CodedInputStream.java:869)
at com.google.protobuf.DescriptorProtos$FileDescriptorProto$Builder.mergeFrom(DescriptorProtos.java:2603)
at com.google.protobuf.DescriptorProtos$FileDescriptorProto$1.parsePartialFrom(DescriptorProtos.java:4517)
at com.google.protobuf.DescriptorProtos$FileDescriptorProto$1.parsePartialFrom(DescriptorProtos.java:4509)
at com.google.protobuf.AbstractParser.parsePartialFrom(AbstractParser.java:77)
at com.google.protobuf.AbstractParser.parseFrom(AbstractParser.java:97)
at com.google.protobuf.DescriptorProtos$FileDescriptorProto$1.parseFrom(DescriptorProtos.java:4509)
at com.google.protobuf.DescriptorProtos$FileDescriptorProto.parseFrom(DescriptorProtos.java:2077)
at com.google.protobuf.Descriptors$FileDescriptor.internalUpdateFileDescriptor(Descriptors.java:505)
at com.google.devtools.cloudtrace.v2.TraceProto.(TraceProto.java:353)
... 8 more