CVE-2026-21716

An incomplete fix for CVE-2024-36137 leaves FileHandle.chmod() and FileHandle.chown() in the promises API without the required permission checks, while their callback-based equivalents (fs.fchmod(), fs.fchown()) were correctly patched.

As a result, code running under --permission with restricted --allow-fs-write can still use promise-based FileHandle methods to modify file permissions and ownership on already-open file descriptors, bypassing the intended write restrictions.

This vulnerability affects 20.x, 22.x, 24.x, and 25.x processes using the Permission Model where --allow-fs-write is intentionally restricted.