# CVE-2026-58091: Kernel use-after-free via the SNDCTL_DSP_SYNCSTART ioctl

> An unprivileged local user can exploit a use-after-free in the FreeBSD kernel audio driver to escalate 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:** 26 Aug 2026
- **Updated:** 27 Aug 2026

## What is CVE-2026-58091?

CVE-2026-58091 is a high-severity use after free vulnerability in Freebsd Freebsd, published on 26 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The implementation of this ioctl attempts to acquire locks on all channels in a sync group.  If locking a channel would block, it releases the sync group list lock and sleeps.  Upon reawakening, it is possible that the sync group structure is freed, but the implementation did not handle this possibility.

 On a system with a multiple audio devices, an unprivileged local user can exploit this use-after-free to escalate privileges.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-58091?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2026-58091?

No fix has been published for CVE-2026-58091 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-58091 being exploited?

There is no known exploitation of CVE-2026-58091 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-2026-58091 and fix it if it is affected.

What it is: CVE-2026-58091 is a high-severity use after free vulnerability in Freebsd Freebsd, published on 26 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-2026-58091 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-2026-58091/ (Markdown: https://insights.sbomify.com/CVE-2026-58091/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58091
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58091
- OSV: https://osv.dev/vulnerability/CVE-2026-58091

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-58091/
Summaries are generated and may contain mistakes; the official description above is the record.