ClassLoaderExt::process_module_table() calls modules_do() which iterates over the ModuleEntryTable without holding Module_lock.
The ModuleEntryTable is not a lock free table as entries can be deleted by concurrent class unloading.

Adding a lock doesn't work because we transition to Native to open a zip file:
V [jvm.dll+0x4f283a] ThreadToNativeFromVM::ThreadToNativeFromVM+0x4a (interfaceSupport.inline.hpp:182)
V [jvm.dll+0x4f33df] ClassLoader::create_class_path_entry+0x7f (classLoader.cpp:742)
V [jvm.dll+0x4f76eb] ClassLoader::setup_module_search_path+0xcb (classLoader.cpp:560)
V [jvm.dll+0xbf13fe] ModuleEntryTable::modules_do+0x5e (moduleEntry.cpp:696)