# CVE-2026-49429: Kernel heap overflow in ZFS_IOC_USERSPACE_MANY ioctl

> A local user with delegated ZFS permissions can trigger a kernel heap overflow via integer truncation, potentially escalating privileges.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Aug 2026
- **Updated:** 20 Aug 2026

## What is CVE-2026-49429?

CVE-2026-49429 is a high-severity vulnerability in Freebsd Freebsd, published on 19 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### 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.

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-49429?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-49429?

No fix has been published for CVE-2026-49429 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-49429 being exploited?

There is no known exploitation of CVE-2026-49429 in the wild and no public exploit code.

## Other vulnerabilities in Freebsd Freebsd

- [CVE-2018-17160](https://insights.sbomify.com/CVE-2018-17160/): Memory corruption in FreeBSD (critical 10.0)
- [CVE-2014-3954](https://insights.sbomify.com/CVE-2014-3954/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-4304](https://insights.sbomify.com/CVE-2006-4304/): Memory corruption in n/a (critical 10.0)
- [CVE-2006-0226](https://insights.sbomify.com/CVE-2006-0226/): Integer overflow in n/a (critical 10.0)
- [CVE-2004-0002](https://insights.sbomify.com/CVE-2004-0002/): Denial of service in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49429 and fix it if it is affected.

What it is: CVE-2026-49429 is a high-severity vulnerability in Freebsd Freebsd, published on 19 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-49429 in the wild and no public exploit code.

Affected product: Freebsd Freebsd. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-49429/ (Markdown: https://insights.sbomify.com/CVE-2026-49429/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49429
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49429
- OSV: https://osv.dev/vulnerability/CVE-2026-49429

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49429/
Summaries are generated and may contain mistakes; the official description above is the record.