CVE-2020-15250

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

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
        // ...
    }
}

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:

1. 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.
2. 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.

A file, directory, or other resource is assigned permissions that allow broader access than intended. Typical impact: unauthorized read, modification, or execution of the resource.

CVE-2020-15250 has a CVSS score of 4.4 (Medium). The vector is requires local access, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.13.1); upgrading removes the vulnerable code path.

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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.

1. What is CVE-2020-15250? CVE-2020-15250 is a medium-severity incorrect permission assignment for critical resource vulnerability in junit:junit (maven), affecting versions >= 4.7, < 4.13.1. It is fixed in 4.13.1. A file, directory, or other resource is assigned permissions that allow broader access than intended.
2. How severe is CVE-2020-15250? CVE-2020-15250 has a CVSS score of 4.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of junit:junit are affected by CVE-2020-15250? junit:junit (maven) versions >= 4.7, < 4.13.1 is affected.
4. Is there a fix for CVE-2020-15250? Yes. CVE-2020-15250 is fixed in 4.13.1. Upgrade to this version or later.
5. Is CVE-2020-15250 exploitable, and should I be worried? Whether CVE-2020-15250 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-15250 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-15250? Upgrade junit:junit to 4.13.1 or later.