Vulnerability · Published Aug 19, 2026 · Assigned by freebsd

CVE-2026-49429Kernel heap overflow in ZFS_IOC_USERSPACE_MANY ioctl

High 7.8

In plain English

A high-severity heap buffer overflow in FreeBSD from FreeBSD. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 4% of all known vulnerabilities).

Severity (CVSS 3.1)7.8High

Exploit odds (30 days)0.2%top 95.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
FreeBSD	FreeBSD	15.1-RELEASE – before p115.0-RELEASE – before p1114.4-RELEASE – before p714.3-RELEASE – before p16

Weakness: CWE-122 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

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