CVE-2023-4759

Arbitrary File Overwrite in Eclipse JGit <= 6.6.0

In Eclipse JGit, all versions <= 6.6.0.202305301015-r, a symbolic link present in a specially crafted git repository can be used to write a file to locations outside the working tree when this repository is cloned with JGit to a case-insensitive filesystem, or when a checkout from a clone of such a repository is performed on a case-insensitive filesystem.

This can happen on checkout (DirCacheCheckout), merge (ResolveMerger via its WorkingTreeUpdater), pull (PullCommand using merge), and when applying a patch (PatchApplier). This can be exploited for remote code execution (RCE), for instance if the file written outside the working tree is a git filter that gets executed on a subsequent git command.

The issue occurs only on case-insensitive filesystems, like the default filesystems on Windows and macOS. The user performing the clone or checkout must have the rights to create symbolic links for the problem to occur, and symbolic links must be enabled in the git configuration.

Setting git configuration option core.symlinks = false before checking out avoids the problem.

The issue was fixed in Eclipse JGit version 6.6.1.202309021850-r and 6.7.0.202309050840-r, available via Maven Central https://repo1.maven.org/maven2/org/eclipse/jgit/  and repo.eclipse.org https://repo.eclipse.org/content/repositories/jgit-releases/ . A backport is available in 5.13.3 starting from 5.13.3.202401111512-r.

The JGit maintainers would like to thank RyotaK for finding and reporting this issue.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Potential Mitigations

• Follow the principle of least privilege when assigning access rights to entities in a software system.
• Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/132.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/35.html
• https://cwe.mitre.org/data/definitions/76.html

References

• https://git.eclipse.org/c/jgit/jgit.git/commit/?id=9072103f3b3cf64dd12ad2949836ab98f62dabf1
• https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/11
• https://projects.eclipse.org/projects/technology.jgit/releases/6.6.1
• https://git.eclipse.org/c/jgit/jgit.git/commit/?id=9072103f3b3cf64dd12ad2949836ab98f62dabf1
• https://gitlab.eclipse.org/security/vulnerability-reports/-/issues/11
• https://projects.eclipse.org/projects/technology.jgit/releases/6.6.1