1. Problem Statement

JNA creates a temporary folder at a known location (harcoded path: /tmp/jna) to do its deed.
Unlike the system's temporary folder, it doesn't set the sticky bit on it... so on multi user systems, several problems arise :

• depending on the umask of the user of the first invocation, the second user might or might not be able to write in the said folder. This materializes as an InvocationTargetException with a root cause of an IOException (as seen on https://stackoverflow.com/questions/8655712/java-error-failed-to-create-temporary-file-for-jnidispatch-library/11461767#11461767 or Fix regression: add relative jna tmpdir path to wrapper if not existing hyphanet/fred#633)
• it creates a security vulnerability (TOCTOU) as highlighted in Review vulnerabilities report #914

2. Suggested changes

I've located at least two separate occurences of the problem:

(runtime error + security vulnerability)
(just a security vulnerability)

In both cases, the easy fix is to make the directory name "instance" specific with an unpredictable path:
https://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#createTempDirectory(java.lang.String,%20java.nio.file.attribute.FileAttribute...)

3. Version information

Seems irrelevant... but it does affect 4.5.1