CVE-2021-29631Public exploit

Guest-to-host code execution via unchecked descriptors

Published Aug 30, 2021 · Updated Aug 3, 2024

Memory corruption in FreeBSD bhyve 11.4-RELEASE before p13, 12.2-RELEASE before p10, and 13.0-RELEASE before p4 allows guest OS users to crash it. VirtIO device-model handlers ignore vq_getchain error returns and then pass uninitialized iovec entries to read, copy, or request-processing operations. With affected VirtIO models attached, crafted guest queues can crash the bhyve process or execute code with that process's privileges.

CVSS severity7.8
High
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in FreeBSD bhyve 11.4-RELEASE before p13, 12.2-RELEASE before p10, and 13.0-RELEASE before p4 allows guest OS users to crash it. VirtIO device-model handlers ignore vq_getchain error returns and then pass uninitialized iovec entries to read, copy, or request-processing operations. With affected VirtIO models attached, crafted guest queues can crash the bhyve process or execute code with that process's privileges.

The record

CVE
CVE-2021-29631
Published
Aug 30, 2021
Updated
Aug 3, 2024
Vendor
The FreeBSD Project
Product
FreeBSD
Classifications
CWE-908, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 30, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=FreeBSD 13.0-RELEASE before p4, 12.2-RELEASE before p10, 11.4-RELEASE before p13

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The FreeBSD Project · FreeBSDversion=FreeBSD 13.0-RELEASE before p4, 12.2-RELEASE before p10, 11.4-RELEASE before p13

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-908Use of Uninitialized Resource
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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