We do not believe this is a security issue; this is a deliberate circumvention of the Javamail API. The Javamail API provides a comprehensive and secure method to retrieve mail. In this example, the author retreives the message directly from the mail directory on the filesystem. Even if the user insists on using this incorrect way of accessing mail, then the permissions set by the dovecot and tomcat packages are enough to protect against direct access to most of the files listed in the bug report.