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CVE Record

CVE-2025-38085: mm/hugetlb: fix huge_pmd_unshare() vs GUP-fast race

In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix huge_pmd_unshare() vs GUP-fast race huge_pmd_unshare() drops a reference on a page table that may have previously been shared across processes, potentially turning it into a normal page table used in another process in which unrelated VMAs can afterwards be installed. If this happens in the middle of a concurrent gup_fast(), gup_fast() could end up walking the page tables of another process. While I don't see any way in which that immediately leads to kernel memory corruption, it is really weird and unexpected. Fix it with an explicit broadcast IPI through tlb_remove_table_sync_one(), just like we do in khugepaged when removing page tables for a THP collapse.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2025-38085 is a Linux kernel memory-management race involving huge pages. In unusual timing, one process could cause kernel page-table walking code to follow another process's page tables. The source text does not claim immediate kernel memory corruption, active exploitation, or a CVSS severity.

Executive priority

Treat as a kernel maintenance priority, not an emergency from the supplied evidence. Schedule patch validation and rollout through normal kernel update channels, with higher priority for shared compute and multi-tenant infrastructure.

Technical view

The bug is in mm/hugetlb: huge_pmd_unshare() can drop a reference to a shared page table while concurrent GUP-fast is walking it. The fix adds explicit synchronization through tlb_remove_table_sync_one(), matching existing THP-collapse handling.

Likely exposure

Exposure is limited to Linux systems running affected kernel builds listed in the CVE record or downstream distributions carrying the vulnerable code. Systems using HugeTLB-related paths are the most relevant validation targets, but the bundle does not quantify prerequisites or reachability.

Exploitation context

The bundle marks KEV as false. It includes upstream stable commits, a Project Zero issue, and Debian LTS advisories, but no cited source states active exploitation, public exploit availability, or confirmed privilege escalation impact.

Researcher notes

Key uncertainty is impact. The upstream description says the behavior is unexpected but does not identify immediate kernel memory corruption. Focus research on race reachability, HugeTLB usage, GUP-fast interaction, and downstream backport status.

Mitigation direction

  • Apply vendor or distribution kernel updates that include the upstream stable fixes.
  • Review Debian LTS advisories if running affected Debian LTS kernels.
  • Check Linux vendor guidance before assuming a specific fixed package version.
  • Prioritize internet-facing, multi-user, container, and virtualization hosts for kernel update review.

Validation and detection

  • Inventory deployed Linux kernel versions across servers, containers hosts, and appliances.
  • Compare kernel builds against the CVE record and vendor security advisories.
  • Confirm whether the relevant upstream stable fix is backported by your distribution.
  • Track reboot completion where kernel package updates require it.
Prepared
Confidence
medium
Sources
12

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-2025-38085 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
11Source 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
LinuxLinux39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa, 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa, 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa, 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa, 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa, 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aa, 39dde65c9940c97fcd178a3d2b1c57ed8b7b68aaunaffected
LinuxLinux2.6.20, 0, 5.10.239, 5.15.186, 6.1.142, 6.6.95, 6.12.35, 6.15.4, 6.16affected
Weakness

CWE details

No CWE listed

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