I just started getting exceptions when I updated my server to the latest Lucee release from v5.1.x to 18.104.22.168. I'm seeing weird exceptions coming through that make no sense at all. For example, the following code occassionally generates the error: For input string: "", which is impossible since the code would never pass the if statement.
After some research, it appears that the java function SimpleDateFormat() is not thread safe. See: https://stackoverflow.com/questions/11368632/multiple-exceptions-thrown-parsing-date-string, and looking at the Lucee source code, LSParseDateTime() calls it.
It also looks like this has been in the Lucee source code since Sep 11, 2015, so this may not be a bug specific to this release.
Windows Server 2012 R2