CVE-2021-32847Public exploit

Host-memory disclosure via malformed DISCARD descriptors

Published Feb 20, 2023 · Updated Mar 10, 2025

Out-of-bounds read in HyperKit 0.20210107 and earlier allows guest OS users to infer host memory through crafted virtio-blk descriptors. In pci_vtblk_proc, an assignment replaces the intended equality test for the DISCARD payload length, so an invalid iov_base reaches structure-field reads. A guest with virtio-blk enabled can use resulting disk-sector changes as an oracle for adjacent host memory; no host code execution is established.

CVSS severity7.1
High
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in HyperKit 0.20210107 and earlier allows guest OS users to infer host memory through crafted virtio-blk descriptors. In pci_vtblk_proc, an assignment replaces the intended equality test for the DISCARD payload length, so an invalid iov_base reaches structure-field reads. A guest with virtio-blk enabled can use resulting disk-sector changes as an oracle for adjacent host memory; no host code execution is established.

The record

CVE
CVE-2021-32847
Published
Feb 20, 2023
Updated
Mar 10, 2025
Vendor
Moby Project
Product
HyperKit
Classifications
CWE-125, T1005
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 20, 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

7.1GitHub, Inc.CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
6.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1005Data from Local System

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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