TemporaryFolder on unix-like systems does not limit access to created files

Vulnerability

PreparedStatement.setText(int, InputStream)
and

PreparedStatemet.setBytea(int, InputStream)

will create a temporary file if the InputStream is larger than 51k

Example of vulnerable code:

String s = "some very large string greater than 51200 bytes";

PreparedStatement.setInputStream(1, new ByteArrayInputStream(s.getBytes()) );

This will create a temporary file which is readable by other users on Unix like systems, but not MacOS.

Impact
On Unix like systems, the system’s temporary directory is shared between all users on that system. Because of this, when files and directories are written into this directory they are, by default, readable by other users on that same system.

This vulnerability does not allow other users to overwrite the contents of these directories or files. This is purely an information disclosure vulnerability.

When analyzing the impact of this vulnerability, here are the important questions to ask:

Is the driver running in an environment where the OS has other untrusted users.
If yes, and you answered ‘yes’ to question 1, this vulnerability impacts you.
If no, this vulnerability does not impact you.
Patches
Because certain JDK file system APIs were only added in JDK 1.7, this this fix is dependent upon the version of the JDK you are using.

Java 1.8 and higher users: this vulnerability is fixed in 42.2.27, 42.3.8, 42.4.3, 42.5.1
Java 1.7 users: this vulnerability is fixed in 42.2.27.jre7
Java 1.6 and lower users: no patch is available; you must use the workaround below.
Workarounds
If you are unable to patch, or are stuck running on Java 1.6, specifying the java.io.tmpdir system environment variable to a directory that is exclusively owned by the executing user will fix this vulnerability.

References
CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
Fix commit https://github.com/pgjdbc/pgjdbc/commit/9008dc9aade6dbfe4efafcd6872ebc55f4699cf5
Similar Vulnerabilities
Google Guava - https://github.com/google/guava/issues/4011
Apache Ant - https://nvd.nist.gov/vuln/detail/CVE-2020-1945
JetBrains Kotlin Compiler - https://nvd.nist.gov/vuln/detail/CVE-2020-15824