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CVE Record

CVE-2021-47018: powerpc/64: Fix the definition of the fixmap area

In the Linux kernel, the following vulnerability has been resolved: powerpc/64: Fix the definition of the fixmap area At the time being, the fixmap area is defined at the top of the address space or just below KASAN. This definition is not valid for PPC64. For PPC64, use the top of the I/O space. Because of circular dependencies, it is not possible to include asm/fixmap.h in asm/book3s/64/pgtable.h , so define a fixed size AREA at the top of the I/O space for fixmap and ensure during build that the size is big enough.

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 issue affecting 64-bit PowerPC systems. It concerns a wrong address-space definition for a special kernel mapping area. The public data does not show confirmed attacks or a severity score, but kernel memory-layout defects deserve attention where PPC64 Linux is used.

Executive priority

Handle as a targeted kernel maintenance item for PPC64 assets, not a broad enterprise emergency. The absence of severity scoring and exploitation evidence lowers urgency, but unsupported or unpatched PPC64 infrastructure should be remediated through normal kernel update processes.

Technical view

The kernel fix changes PPC64 fixmap placement from the top of address space or below KASAN to the top of I/O space. It also defines a fixed-size fixmap area and adds a build-time size check. The source bundle does not describe impact mechanics, privilege requirements, or exploit primitives.

Likely exposure

Exposure appears limited to Linux deployments on 64-bit PowerPC using affected kernel versions or downstream kernels missing the referenced stable commits. The bundle lists Linux 5.5 through 5.13-related affected data, including fixes for 5.10.37, 5.11.21, and 5.12.4 contexts.

Exploitation context

No provided source indicates active exploitation, KEV inclusion, public exploit availability, or weaponized use. Treat exploitation status as unconfirmed. Research should focus on whether downstream PPC64 kernels incorporated the stable fix and whether local conditions expose the faulty fixmap layout.

Researcher notes

The public description is sparse and only states the resolved implementation defect. There is no CWE, CVSS, exploit detail, or impact narrative in the bundle. Avoid assuming confidentiality, integrity, availability, or privilege-escalation impact without additional vendor analysis.

Mitigation direction

  • Identify Linux systems running 64-bit PowerPC kernels.
  • Check vendor kernel advisories for CVE-2021-47018 coverage.
  • Update affected kernels to vendor builds containing the stable fix.
  • Prioritize PPC64 production, virtualization, and appliance-like systems.
  • If patching is delayed, follow vendor-specific compensating guidance.

Validation and detection

  • Confirm each system architecture is PPC64 before scoping exposure.
  • Map running kernel builds to vendor-fixed releases or referenced commits.
  • Review distribution backport notes, not only upstream version numbers.
  • Verify change management records show the fixed kernel deployed.
  • Track unknown-severity status separately from scored kernel issues.
Prepared
Confidence
medium
Sources
6

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-2021-47018 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
5Source 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

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux265c3491c4bc8d40587996d6ee2f447a7ccfb4f3, 265c3491c4bc8d40587996d6ee2f447a7ccfb4f3, 265c3491c4bc8d40587996d6ee2f447a7ccfb4f3, 265c3491c4bc8d40587996d6ee2f447a7ccfb4f3unaffected
LinuxLinux5.5, 0, 5.10.37, 5.11.21, 5.12.4, 5.13affected
Weakness

CWE details

No CWE listed

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