bhyve privileged guest escape via fwctl

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.

Timeline

Scores

EPSS (exploitation in 30 days)

0.23% · top 86% of all CVEs (7 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.

Weakness

• CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') (opens in a new tab)All about CWE-120 and its CVEs

Affected products

• FreeBSD · FreeBSD

  • affected 13.2-RELEASE – < 13.2-RELEASE-p2
  • affected 13.1-RELEASE – < 13.1-RELEASE-p9

References (2)

• https://security.FreeBSD.org/advisories/FreeBSD-SA-23:07.bhyve.asc (opens in a new tab)vendor-advisoryx_transferred
• https://security.netapp.com/advisory/ntap-20230831-0006/ (opens in a new tab)x_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2023-3494](https://trackcve.app/badge/CVE-2023-3494.svg)](https://trackcve.app/cve/CVE-2023-3494)

Record last updated 13 Feb 2025, 16:55 UTC.