Description
When fdescfs(4) was mounted in a jail with the "nodup" option, opening /dev/fd/N returned a descriptor that did not inherit FD_RESOLVE_BENEATH or the Capsicum capability rights of descriptor N.
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| FreeBSD | FreeBSD | 15.1-RELEASE – < p4, 15.0-RELEASE – < p14, 14.5-RELEASE – < p1, 14.4-RELEASE – < p10 | p4 |
Advisories 1
- WID-SEC-2026-3664 FreeBSD Project FreeBSD OS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 14, 2026