renameat(2) did not enforce FD_RESOLVE_BENEATH on its directory arguments. A jailed process could rename a directory relative to a restricted descriptor, then escape the jail root via fchdir(2). This requires the directory to reside on a filesystem that is also reachable from the jail's root.
A process in a jail that has received a directory file descriptor from another jail can use these techniques to escape the jail's filesystem root restriction.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Freebsd | — | Upgrade FreeBSD | Oct 5, 2026 | Sep 30, 2026 |
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