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

Moderate severity GitHub Reviewed Published Oct 11, 2020 in junit-team/junit4 • Updated Feb 1, 2023

Package

maven junit:junit (Maven)

Affected versions

>= 4.7, < 4.13.1

Patched versions

4.13.1

Description

Vulnerability

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

Example of vulnerable code:

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:

  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.

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

For more information

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

References

@marcphilipp marcphilipp published to junit-team/junit4 Oct 11, 2020
Reviewed Oct 12, 2020
Published to the GitHub Advisory Database Oct 12, 2020
Published by the National Vulnerability Database Oct 12, 2020
Last updated Feb 1, 2023

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N

EPSS score

0.076%
(34th percentile)

CVE ID

CVE-2020-15250

GHSA ID

GHSA-269g-pwp5-87pp

Source code

Credits

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