CVE-2026-39822

On Unix systems, opening a file in an os.Root improperly follows symlinks to locations outside of the Root when the final path component of the a path is a symbolic link and the path ends in /. For example, root.Open(symlink/) will open symlink even when symlink is a symbolic link pointing outside of the root.

Weakness

The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

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/27.html

References

• https://go.dev/cl/797880
• https://go.dev/issue/79005
• https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc
• https://pkg.go.dev/vuln/GO-2026-4970