CVE-2026-56857

On Windows, when the target of Root.Mkdir or Root.MkdirAll is a junction pointing to an empty location, the operation can create a directory at the junction target even when that target is located outside the root. This only applies to operations where the last path component is a junction (path/to/junction, but not path/junction/target).

Weakness

The product opens a file or directory, but it does not properly prevent the name from being associated with a junction or mount point to a destination that is outside of the intended control sphere.

Affected Software

Extended Description

Depending on the intended action being performed, this could allow an attacker to cause the product to read, write, delete, or otherwise operate on unauthorized files. In Windows, NTFS5 allows for file system objects called reparse points. Applications can create a hard link from one directory to another directory, called a junction point. They can also create a mapping from a directory to a drive letter, called a mount point. If a file is used by a privileged program, but it can be replaced with a hard link to a sensitive file (e.g., AUTOEXEC.BAT), an attacker could escalate privileges. When the process opens the file, the attacker can assume the privileges of that process, tricking the privileged process to read, modify, or delete the sensitive file, preventing the program from accurately processing data. Note that one can also point to registries and semaphores.

Potential Mitigations

References

• https://go.dev/cl/847305
• https://go.dev/issue/81739
• https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
• https://pkg.go.dev/vuln/GO-2026-6604