java.lang.VersionProps defines a number of JDK version properties that are read by the VM and stored in JDK_Version or VM_Version. These values are read into fixed size buffers (thread.cpp):

char java_version[64] = "";
char java_runtime_name[128] = "";
char java_runtime_version[128] = "";
char java_runtime_vendor_version[128] = "";
char java_runtime_vendor_vm_bug_url[128] = "";

There is no guarantee that the value being read actually fits in these buffers.

Update: we can bypass these buffers altogether - see comments