We have seen several instances of this exception during application startup. The first encountered was of the form:
```
2024-01-14 12:08:05.800,"Caused by: java.lang.BootstrapMethodError: java.lang.NullPointerException: Cannot invoke ""java.lang.Module.isExported(String)"" because ""refModule"" is null"
2024-01-14 12:08:05.800, at java.base/sun.util.cldr.CLDRLocaleProviderAdapter.<init>(CLDRLocaleProviderAdapter.java:85)
```
Which has this code on that line:
```
nbmi = AccessController.doPrivileged((PrivilegedExceptionAction<LocaleDataMetaInfo>) () -> {
```
https://github.com/openjdk/jdk17u-dev/blob/master/src/java.base/share/classes/sun/util/cldr/CLDRLocaleProviderAdapter.java#L85

Erroneously believing this to be a problem with CLDRLocaleProviderAdapter, we tried using the JRE provider with: `-Djava.locale.providers=JRE,CLDR` but this only changed which caller encounters the exception:

```
2024-05-04 15:42:02.149: Caused by: java.lang.BootstrapMethodError: java.lang.NullPointerException: Cannot invoke "java.lang.Module.isExported(String)" because "refModule" is null
2024-05-04 15:42:02.149: at sun.util.locale.provider.JRELocaleProviderAdapter.getTimeZoneNameProvider(JRELocaleProviderAdapter.java:301) ~[?:?]
```
However, the code here is also trying to perform a privileged action:
```
TimeZoneNameProvider provider = AccessController.doPrivileged(
```

https://github.com/openjdk/jdk17u-dev/blob/master/src/java.base/share/classes/sun/util/locale/provider/JRELocaleProviderAdapter.java#L301

This happens rarely and always near application startup. We do not have a reproducer yet. It feels like an initialization race within the module system, but I'm no expert here.