CVE-2021-32844Public exploit

Host crash via unchecked Virtio write handler

Published Feb 17, 2023 · Updated Mar 10, 2025

NULL pointer dereference in HyperKit 0.20210107 and earlier allows guest OS users to crash the host through a Virtio RNG PCI write. The vi_pci_write function invokes the vtrnd device's absent vc_cfgwrite handler without checking it for NULL, transferring control to address zero. Reaching the flaw requires control of a guest configured with virtio-rnd; exploitation terminates the host hypervisor and interrupts its guests.

CVSS severity6.2
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in HyperKit 0.20210107 and earlier allows guest OS users to crash the host through a Virtio RNG PCI write. The vi_pci_write function invokes the vtrnd device's absent vc_cfgwrite handler without checking it for NULL, transferring control to address zero. Reaching the flaw requires control of a guest configured with virtio-rnd; exploitation terminates the host hypervisor and interrupts its guests.

The record

CVE
CVE-2021-32844
Published
Feb 17, 2023
Updated
Mar 10, 2025
Vendor
Moby Project
Product
HyperKit
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 17, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 10, 2025Record 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=0.20210107 <=0.20210107

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Moby Project · HyperKitversion=0.20210107 <=0.20210107

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.2GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

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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