CVE-2026-49429

High

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.

SeverityHigh

CVSS7.8

Exploit probability—

Product

Freebsd

PublishedAug 19, 2026

First seenAug 19, 2026

Weakness typeCWE-122CWE-122

How to fix

Vendor advisories

security.freebsd.org/advisories/FreeBSD-SA-26:40.zfs.asc

Affected products

Product	Affected versions	Fixed in
freebsd freebsd	14.3, 14.4, 15.0, 15.1	—

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