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CVE Record

CVE-2021-47429: powerpc/64s: Fix unrecoverable MCE calling async handler from NMI

In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Fix unrecoverable MCE calling async handler from NMI The machine check handler is not considered NMI on 64s. The early handler is the true NMI handler, and then it schedules the machine_check_exception handler to run when interrupts are enabled. This works fine except the case of an unrecoverable MCE, where the true NMI is taken when MSR[RI] is clear, it can not recover, so it calls machine_check_exception directly so something might be done about it. Calling an async handler from NMI context can result in irq state and other things getting corrupted. This can also trigger the BUG at arch/powerpc/include/asm/interrupt.h:168 BUG_ON(!arch_irq_disabled_regs(regs) && !(regs->msr & MSR_EE)); Fix this by making an _async version of the handler which is called in the normal case, and a NMI version that is called for unrecoverable interrupts.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel flaw affecting PowerPC 64-bit server code during unrecoverable machine-check errors. The handler could corrupt interrupt state and trigger a kernel BUG, likely causing system instability or crash. The available sources do not provide CVSS, active exploitation, or a complete vendor remediation matrix.

Executive priority

Treat this as a targeted infrastructure reliability issue for PowerPC Linux estates. It is not currently supported as actively exploited, but unpatched critical PowerPC workloads could face crash risk under machine-check conditions.

Technical view

On powerpc/64s, an unrecoverable machine check could call the asynchronous machine_check_exception handler from true NMI context when MSR[RI] is clear. That unsafe context transition could corrupt IRQ state and hit a BUG in arch/powerpc/include/asm/interrupt.h. The fix separates async and NMI handler paths.

Likely exposure

Exposure appears limited to Linux systems running affected PowerPC 64s kernels, with source data naming Linux 5.14, 5.14.12, and 5.15-related version entries. x86 or non-PowerPC deployments are not indicated by the supplied sources.

Exploitation context

CISA KEV status is false, and the supplied sources do not report active exploitation. The described trigger is an unrecoverable machine-check path, so the practical impact is likely availability or kernel stability rather than a remotely weaponized scenario, based only on available evidence.

Researcher notes

The public record is sparse: no CVSS, CWE, exploit report, or detailed affected matrix is provided. Analysis should focus on kernel branch ancestry, distro backports, and whether the NMI-specific handler split is present in deployed PowerPC 64s builds.

Mitigation direction

  • Update affected PowerPC 64s Linux kernels through the normal vendor or distribution channel.
  • Confirm the update includes the referenced upstream stable fixes.
  • Prioritize systems where PowerPC hosts support critical workloads or high availability services.
  • If no package is available, track vendor guidance for backports or mitigations.
  • Avoid unsupported kernel workarounds unless your platform vendor recommends them.

Validation and detection

  • Inventory Linux hosts by CPU architecture and kernel version.
  • Identify PowerPC 64s systems in the affected kernel range.
  • Check vendor changelogs for commits d7a8e38999fb or f08fb25bc669.
  • Review kernel logs for machine-check exceptions or related BUG messages.
  • Confirm patched systems rebooted into the corrected kernel.
Prepared
Confidence
medium
Sources
4

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

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CVE-2021-47429 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
3Source 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
LinuxLinux2b43dd7653cca47d297756980846ebbfe8887fa1, 2b43dd7653cca47d297756980846ebbfe8887fa1unaffected
LinuxLinux5.14, 0, 5.14.12, 5.15affected
Weakness

CWE details

No CWE listed

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