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CVE Record

CVE-2021-47016: m68k: mvme147,mvme16x: Don't wipe PCC timer config bits

In the Linux kernel, the following vulnerability has been resolved: m68k: mvme147,mvme16x: Don't wipe PCC timer config bits Don't clear the timer 1 configuration bits when clearing the interrupt flag and counter overflow. As Michael reported, "This results in no timer interrupts being delivered after the first. Initialization then hangs in calibrate_delay as the jiffies counter is not updated." On mvme16x, enable the timer after requesting the irq, consistent with mvme147.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel issue affecting specific m68k VME systems. A timer configuration bug can stop timer interrupts after the first interrupt, causing initialization to hang because the kernel time counter is not updated. The available sources describe an availability problem, not data theft or remote code execution.

Executive priority

Treat as a targeted operational reliability issue for legacy m68k environments. It is not flagged as exploited and has no CVSS score in the bundle, but affected systems may fail to initialize correctly. Prioritize based on presence of these platforms and business reliance on them.

Technical view

On m68k mvme147 and mvme16x, clearing the PCC timer interrupt flag also cleared timer configuration bits. That could stop further timer interrupts and hang during calibrate_delay when jiffies stops advancing. The fix preserves timer configuration bits and aligns mvme16x timer enable ordering with mvme147.

Likely exposure

Exposure appears limited to Linux systems using the m68k mvme147 or mvme16x platforms and affected kernel versions or commits listed in the CVE data. Most modern Linux fleets are unlikely to run this hardware, but embedded, industrial, or legacy VME deployments should verify.

Exploitation context

The bundle marks KEV as false and provides no evidence of active exploitation or public exploit activity. The described failure mode is operational availability during initialization, not a demonstrated attacker-driven exploit path. Evidence is incomplete on attack prerequisites and real-world exploitability.

Researcher notes

The CVE record describes a kernel bug fix rather than an exploit primitive. Key evidence is the stable kernel commit set and the failure description: timer interrupts stop after the first event, jiffies does not update, and initialization hangs in calibrate_delay.

Mitigation direction

  • Identify any Linux m68k mvme147 or mvme16x systems in inventory.
  • Compare deployed kernels against the CVE affected versions and stable fix references.
  • Apply the relevant upstream or vendor-provided Linux kernel update.
  • For appliances, request vendor confirmation that the fixed kernel change is included.
  • Prioritize remediation for systems where reboot failure affects operations.

Validation and detection

  • Confirm whether mvme147 or mvme16x platform support is enabled or deployed.
  • Check kernel version and downstream patch level against the referenced stable commits.
  • Review boot logs for timer interrupt or calibrate_delay hang symptoms.
  • Validate vendor advisories before assuming a downstream package contains the fix.
  • After patching, reboot a representative test system and confirm normal timer behavior.
Prepared
Confidence
medium
Sources
7

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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CVE-2021-47016 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
2ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux7529b90d051e4629884771ba2b1d3a87d2c6a9d7, 7529b90d051e4629884771ba2b1d3a87d2c6a9d7, 7529b90d051e4629884771ba2b1d3a87d2c6a9d7, 7529b90d051e4629884771ba2b1d3a87d2c6a9d7, 7529b90d051e4629884771ba2b1d3a87d2c6a9d7unaffected
LinuxLinux5.2, 0, 5.4.119, 5.10.37, 5.11.21, 5.12.4, 5.13affected
Weakness

CWE details

No CWE listed

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