# CVE-2026-45251: Kernel use-after-free via file descriptor syscalls

> An unprivileged local user can exploit a use-after-free in the FreeBSD kernel to gain superuser 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:** 21 May 2026
- **Updated:** 22 May 2026
- **Also known as:** GHSA-wp9w-fp98-2cxm

## What is CVE-2026-45251?

CVE-2026-45251 is a high-severity use after free vulnerability in Freebsd Freebsd, published on 21 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A file descriptor can be closed while a thread is blocked in a poll(2) or select(2) call waiting for that descriptor.  Because the blocked thread does not hold a reference to the underlying object, this closure may result in the object being freed while the thread remains blocked.  In this situation, the kernel must remove the blocked thread from the per-object wait queue prior to freeing the object.

In the case of some file descriptor types, the kernel failed to unlink blocked threads from the object before freeing it.  When the blocked thread is subsequently woken, it accesses memory that has already been freed resulting in a use-after-free vulnerability.

The use-after-free vulnerability may be triggered by an unprivileged local user and can be exploited to obtain superuser privileges.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-45251?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-45251?

No fix has been published for CVE-2026-45251 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-45251 being exploited?

There is no known exploitation of CVE-2026-45251 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-2026-45251 and fix it if it is affected.

What it is: CVE-2026-45251 is a high-severity use after free vulnerability in Freebsd Freebsd, published on 21 May 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-2026-45251 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-2026-45251/ (Markdown: https://insights.sbomify.com/CVE-2026-45251/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45251
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45251
- OSV: https://osv.dev/vulnerability/CVE-2026-45251

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45251/
Summaries are generated and may contain mistakes; the official description above is the record.