# CVE-2023-3494: bhyve privileged guest escape via fwctl

> A privileged guest VM can exploit a buffer overflow in the bhyve fwctl driver to execute arbitrary code on the host, potentially bypassing Capsicum sandboxing.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/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:** 1 Aug 2023
- **Updated:** 13 Feb 2025
- **Also known as:** GHSA-6672-m2hq-hwm4

## What is CVE-2023-3494?

CVE-2023-3494 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 1 Aug 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

The fwctl driver implements a state machine which is executed when a bhyve guest accesses certain x86 I/O ports.  The interface lets the guest copy a string into a buffer resident in the bhyve process' memory.  A bug in the state machine implementation can result in a buffer overflowing when copying this string. Malicious, privileged software running in a guest VM can exploit the buffer overflow to achieve code execution on the host in the bhyve userspace process, which typically runs as root, mitigated by the capabilities assigned through the Capsicum sandbox available to the bhyve process.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2023-3494?

It affects 1 product.


Products: Freebsd Freebsd.

## How do I fix CVE-2023-3494?

No fix has been published for CVE-2023-3494 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-3494 being exploited?

There is no known exploitation of CVE-2023-3494 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-2023-3494 and fix it if it is affected.

What it is: CVE-2023-3494 is a high-severity memory corruption vulnerability in Freebsd Freebsd, published on 1 Aug 2023. 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-2023-3494 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-2023-3494/ (Markdown: https://insights.sbomify.com/CVE-2023-3494/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-3494
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-3494
- OSV: https://osv.dev/vulnerability/CVE-2023-3494

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-3494/
Summaries are generated and may contain mistakes; the official description above is the record.