CVE-2021-47016

Boot hang via cleared PCC timer configuration

Published Feb 29, 2024 · Updated May 11, 2026

Denial of service in the m68k PCC timer code in Linux allows local users to hang system initialization on affected MVME systems. The interrupt handler clears timer configuration bits while acknowledging the interrupt flag and counter overflow, preventing delivery of subsequent timer interrupts. Reachability is limited to MVME147 or MVME16x hardware using the affected kernel code, where the stalled jiffies counter leaves calibrate_delay unable to finish.

CVSS severity5.5
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the m68k PCC timer code in Linux allows local users to hang system initialization on affected MVME systems. The interrupt handler clears timer configuration bits while acknowledging the interrupt flag and counter overflow, preventing delivery of subsequent timer interrupts. Reachability is limited to MVME147 or MVME16x hardware using the affected kernel code, where the stalled jiffies counter leaves calibrate_delay unable to finish.

The record

CVE
CVE-2021-47016
Published
Feb 29, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 29, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=5.2
  2. Affected versionversion=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <1dfb26df15fc7036a74221d43de7427f74293dae
  3. Affected versionversion=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <43262178c043032e7c42d00de44c818ba05f9967
  4. Affected versionversion=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <5d34225169346cab5145978d153b9ce90e9ace21
  5. Affected versionversion=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <73fdeb612d25b5e105c219e05434285a45d23576
  6. Affected versionversion=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <f6a90818a32058fca62cda3a2027a6a2364e1878

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.2; version=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <1dfb26df15fc7036a74221d43de7427f74293dae; version=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <43262178c043032e7c42d00de44c818ba05f9967; version=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <5d34225169346cab5145978d153b9ce90e9ace21; version=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <73fdeb612d25b5e105c219e05434285a45d23576; version=7529b90d051e4629884771ba2b1d3a87d2c6a9d7 <f6a90818a32058fca62cda3a2027a6a2364e1878

Published CVSS scores

5.5NIST NVDCVSS: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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