This issue is related to JENKINS-9486. If the libjna-java package is installed on the system via apt-get, the patched version of libjna-java introduced via JENKINS-9486 is not used and the unpatched system version is used instead. In that case, a login attempt results in the attached exception. A fix could involve catching the exception and displaying a more meaningful error message with instructions to remove the unpatched libjna-java library from the classpath.