Medium

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

Disclosed: 12.10.2020
Updated: 11.10.2026 13:19

Vulnerability

The JUnit4 test rule TemporaryFolder contains a local information disclosure vulnerability.

Example of vulnerable code:

java

public static class HasTempFolder {
    @Rule
    public TemporaryFolder folder = new TemporaryFolder();

    @Test
    public void testUsingTempFolder() throws IOException {
        folder.getRoot(); // Previous file permissions: `drwxr-xr-x`; After fix:`drwx------`
        File createdFile= folder.newFile("myfile.txt"); // unchanged/irrelevant file permissions
        File createdFolder= folder.newFolder("subfolder"); // unchanged/irrelevant file permissions
        // ...
    }
}

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:

Do the JUnit tests write sensitive information, like API keys or passwords, into the temporary folder?
- If yes, this vulnerability impacts you, but only if you also answer 'yes' to question 2.
- If no, this vulnerability does not impact you.
Do the JUnit tests ever execute in an environment where the OS has other untrusted users. This may apply in CI/CD environments but normally won't be 'yes' for personal developer machines.
- 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 1.7 and higher users: this vulnerability is fixed in 4.13.1.
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

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

For more information

If you have any questions or comments about this advisory, please pen an issue in junit-team/junit4.

Affected software

Click a technology to see all vulnerabilities affecting it.

Platform	Package	Vulnerable versions	Fixed in
Java / Kotlin (Maven)	junit:junit	>= 4.7, < 4.13.1	4.13.1

References

CVSS score 4.4/10

CVSS vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N
Weakness (CWE): CWE-200, CWE-732
Platform: Java / Kotlin (Maven)
Package: junit:junit
Disclosed: 12.10.2020
Updated: 11.10.2026 13:19

Sources and licenses

OSV / GitHub Advisory Database - GHSA-269g-pwp5-87pp - CC BY 4.0

Vulnerability history: junit:junit

All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.

This is the only known vulnerability of this package.

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

Vulnerability

Impact

Patches

Workarounds

References

Similar Vulnerabilities

For more information

Affected software

References

Vulnerability history: junit:junit

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