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.
Published: 2026-08-19
Score: 7.8 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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Remediation

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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

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: 2026-08-19T20:00:05Z

Weaknesses