CVE-2021-47217

Kernel crash via unchecked virtual-processor index

Published Apr 10, 2024 · Updated May 11, 2026

NULL pointer dereference in affected Linux kernel releases allows local users to crash the kernel after failed Hyper-V setup. set_hv_tscchange_cb() reads hv_vp_index without checking whether hyperv_init() left the array unallocated while the kernel still reports Hyper-V. Later KVM or VMX initialization can invoke the callback and cause a supervisor-mode page fault and kernel Oops, interrupting the system.

CVSS severity5.5
Medium
EPSS probability0.24%
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 affected Linux kernel releases allows local users to crash the kernel after failed Hyper-V setup. set_hv_tscchange_cb() reads hv_vp_index without checking whether hyperv_init() left the array unallocated while the kernel still reports Hyper-V. Later KVM or VMX initialization can invoke the callback and cause a supervisor-mode page fault and kernel Oops, interrupting the system.

The record

CVE
CVE-2021-47217
Published
Apr 10, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 10, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record 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=4.16
  2. Affected versionversion=93286261de1b46339aa27cd4c639b21778f6cade <8823ea27fff6084bbb4bc71d15378fae0220b1d8
  3. Affected versionversion=93286261de1b46339aa27cd4c639b21778f6cade <9c177eee116cf888276d3748cb176e72562cfd5c
  4. Affected versionversion=93286261de1b46339aa27cd4c639b21778f6cade <b0e44dfb4e4c699cca33ede431b8d127e6e8d661
  5. Affected versionversion=93286261de1b46339aa27cd4c639b21778f6cade <b20ec58f8a6f4fef32cc71480ddf824584e24743
  6. Affected versionversion=93286261de1b46339aa27cd4c639b21778f6cade <daf972118c517b91f74ff1731417feb4270625a4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.16; version=93286261de1b46339aa27cd4c639b21778f6cade <8823ea27fff6084bbb4bc71d15378fae0220b1d8; version=93286261de1b46339aa27cd4c639b21778f6cade <9c177eee116cf888276d3748cb176e72562cfd5c; version=93286261de1b46339aa27cd4c639b21778f6cade <b0e44dfb4e4c699cca33ede431b8d127e6e8d661; version=93286261de1b46339aa27cd4c639b21778f6cade <b20ec58f8a6f4fef32cc71480ddf824584e24743; version=93286261de1b46339aa27cd4c639b21778f6cade <daf972118c517b91f74ff1731417feb4270625a4

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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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