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CVE Record

CVE-2021-32847: Moby HyperKit uninitialized memory use in virtio-sock pci_vtsock_proc_tx

HyperKit is a toolkit for embedding hypervisor capabilities in an application. In versions 0.20210107 and prior, a malicious guest can trigger a vulnerability in the host by abusing the disk driver that may lead to the disclosure of the host memory into the virtualized guest. This issue is fixed in commit cf60095a4d8c3cb2e182a14415467afd356e982f.

HighCVSS 7.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A malicious virtual machine guest could make HyperKit expose host memory back into the guest. The business impact is confidentiality: secrets, process data, or other sensitive host memory could be disclosed if vulnerable HyperKit is used with attacker-controlled guests.

Executive priority

Treat this as a high-priority confidentiality issue for virtualization environments using HyperKit with untrusted guests. It is less urgent where HyperKit is absent or only trusted local guests are used, but affected hosts should still be patched through vendor-supported updates.

Technical view

CVE-2021-32847 affects Moby HyperKit 0.20210107 and prior. The sources describe an out-of-bounds or uninitialized-memory disclosure in host-side virtual device handling, fixed by commit cf60095a4d8c3cb2e182a14415467afd356e982f. CVSS 3.1 is 7.1 with local attack vector, low complexity, changed scope, and high confidentiality impact.

Likely exposure

Exposure is most likely where Moby HyperKit 0.20210107 or earlier is embedded and runs guest VMs that may be malicious or untrusted. The supplied sources do not identify downstream products beyond Moby HyperKit.

Exploitation context

The CVSS vector indicates local access from a guest context, no privileges, no user interaction, and confidentiality-only impact. The provided bundle says CISA KEV is false and includes no cited evidence of active exploitation.

Researcher notes

There is a source inconsistency: the title references virtio-sock pci_vtsock_proc_tx, while the description and code reference point to disk-driver handling in pci_virtio_block.c. Rely on the advisory and fixed commit when validating the affected code path.

Mitigation direction

  • Upgrade HyperKit to a build containing commit cf60095a4d8c3cb2e182a14415467afd356e982f.
  • Check vendor or downstream maintainer guidance for packaged HyperKit updates.
  • Avoid running untrusted guest VMs on vulnerable HyperKit hosts until remediated.
  • Prioritize hosts where guest workloads are tenant-controlled or externally supplied.

Validation and detection

  • Inventory systems and products embedding Moby HyperKit.
  • Confirm HyperKit is newer than 0.20210107 or includes the fixed commit.
  • Review SBOMs, build metadata, and vendor package notes for HyperKit provenance.
  • Identify whether any vulnerable hosts run untrusted or attacker-controlled guest VMs.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-125: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-32847 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.1CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N2.54Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.1High
CVSS 3.1 vector shape for CVE-2021-32847Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
mobyhyperkit0.20210107Listed
Weakness

CWE details

CWE-125

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-125 · source CWE mapping

Out-of-bounds Read

Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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