A flaw in Node.js Permission Model filesystem enforcement leaves `fs.realpathSync()` without the required read permission checks. This is an incomplete fix of CVE-2026-21715, which only covered `fs.realpathSync.native()`.
As a result, code running under `--permission` with restricted `--allow-fs-read` can still use `fs.realpathSync()` to check file existence, resolve symlink targets, and enumerate filesystem paths outside of permitted directories.
This vulnerability affects Node.js **26.x**, **24.x**, and **22.x**.