LiveActive security incident?Get immediate response
CVE Record

CVE-2021-47214: hugetlb, userfaultfd: fix reservation restore on userfaultfd error

In the Linux kernel, the following vulnerability has been resolved: hugetlb, userfaultfd: fix reservation restore on userfaultfd error Currently in the is_continue case in hugetlb_mcopy_atomic_pte(), if we bail out using "goto out_release_unlock;" in the cases where idx >= size, or !huge_pte_none(), the code will detect that new_pagecache_page == false, and so call restore_reserve_on_error(). In this case I see restore_reserve_on_error() delete the reservation, and the following call to remove_inode_hugepages() will increment h->resv_hugepages causing a 100% reproducible leak. We should treat the is_continue case similar to adding a page into the pagecache and set new_pagecache_page to true, to indicate that there is no reservation to restore on the error path, and we need not call restore_reserve_on_error(). Rename new_pagecache_page to page_in_pagecache to make that clear.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel flaw can mishandle huge-page reservation accounting when a userfaultfd operation errors. The described outcome is a reproducible reservation leak, which can affect host resource accounting and reliability rather than exposing data directly in the provided record.

Executive priority

Treat as a kernel reliability issue with incomplete severity data. Prioritize patching where affected kernels support critical workloads, virtualization, databases, or memory-heavy services.

Technical view

CVE-2021-47214 concerns hugetlb_mcopy_atomic_pte() in the hugetlb and userfaultfd path. In the is_continue case, error handling could call restore_reserve_on_error() even though no reservation should be restored, leading to incorrect h->resv_hugepages accounting. The kernel fix treats that path as page-in-pagecache behavior.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions listed in the CVE record and exercising hugetlb/userfaultfd paths. Distribution backports may change exposure, so kernel package advisory mapping is required.

Exploitation context

The source bundle does not report active exploitation, public exploit availability, or CISA KEV listing. It describes a reproducible leak in a kernel error path, but does not provide business-impact evidence beyond resource accounting failure.

Researcher notes

The record names no CWE, CVSS, or exploit status. Analysis should focus on confirming affected kernel lineage and whether the stable commits are present, not assuming privilege escalation or remote reachability.

Mitigation direction

  • Check vendor or distribution advisories for CVE-2021-47214 kernel fixes.
  • Update affected Linux kernels to versions containing the referenced stable fixes.
  • Prioritize hosts using huge pages, userfaultfd, or memory-intensive workloads.
  • Track this through standard kernel patch management if exposure is uncertain.

Validation and detection

  • Inventory Linux kernel versions across servers, containers hosts, and appliances.
  • Map distro kernel builds to the upstream stable commits in the references.
  • Review whether hugetlb and userfaultfd are used on exposed systems.
  • Confirm patched systems include the corrected hugetlb/userfaultfd reservation handling.
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

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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2021-47214 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
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
LinuxLinuxc7b1850dfb41d0b4154aca8dbc04777fbd75616f, c7b1850dfb41d0b4154aca8dbc04777fbd75616f, 515b6124df6a84c957c5cc6bb6e8309dae7b1e9cunaffected
LinuxLinux5.14, 0, 5.15.5, 5.16affected
Weakness

CWE details

No CWE listed

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