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.

Project Subscriptions

Vendors Products
Freebsd Subscribe
Freebsd Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 19 Aug 2026 13:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}


Wed, 19 Aug 2026 12:45:00 +0000

Type Values Removed Values Added
First Time appeared Freebsd
Freebsd freebsd
Vendors & Products Freebsd
Freebsd freebsd

Wed, 19 Aug 2026 05:30:00 +0000

Type Values Removed Values Added
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.
Title Kernel heap overflow in ZFS_IOC_USERSPACE_MANY ioctl
Weaknesses CWE-122
References

Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: freebsd

Published:

Updated: 2026-08-19T12:16:35.367Z

Reserved: 2026-05-29T20:24:28.616Z

Link: CVE-2026-49429

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-19T06:17:42.513

Modified: 2026-08-19T13:17:46.030

Link: CVE-2026-49429

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-19T12:30:04Z

Weaknesses