Description
The ZFS_IOC_USERSPACE_MANY ioctl, used by zfs-userspace(8), truncated a 64-bit output buffer size to a 32-bit integer for the kernel allocation, but used the original 64-bit size as the buffer limit when writing records.
A local user with the "userused" delegated ZFS permission can trigger a kernel heap overflow via the ZFS_IOC_USERSPACE_MANY ioctl, potentially escalating privileges.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| FreeBSD | FreeBSD | 15.1-RELEASE – < p1, 15.0-RELEASE – < p11, 14.4-RELEASE – < p7, 14.3-RELEASE – < p16 | p1 |
Advisories 1
- WID-SEC-2026-2165 FreeBSD Project FreeBSD OS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Aug 19, 2026
References
- https://security.freebsd.org/advisories/FreeBSD-SA-26:40.zfs.asc vendor-advisory