Path traversal by monkey-patching Buffer internals

Summary

The permission model protects itself against path traversal attacks by calling path.resolve() on any paths given by the user. If the path is to be treated as a Buffer, the implementation uses Buffer.from() to obtain a Buffer from the result of path.resolve(). By monkey-patching Buffer internals, namely, Buffer.prototype.utf8Write, the application can modify the result of path.resolve(), which leads to a path traversal vulnerability.

This vulnerability affects all users using the experimental permission model in Node.js 20 and Node.js 21.

Please note that at the time this CVE was issued, the permission model is an experimental feature of Node.js.