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CVE-2026-74632 Linux CVE debrief

A race condition vulnerability in the Linux kernel's mm/huge_memory module has been identified. The issue arises from the improper synchronization of the huge_zero_pfn variable, which can lead to incorrect identification of huge zero folios as ordinary THP folios. This can result in the huge zero folio being split and treated incorrectly. The vulnerability is caused by a subtle race condition in the reference-counted huge_zero_folio implementation. The fast path atomic logic fails to account for the fact that the shrinker can overwrite huge_zero_pfn with the ~0UL sentinel value after a racing get_huge_zero_folio installed a valid value there. Linux system administrators and related

Vendor
Linux
Product
Unknown
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-22
Original CVE updated
2026-10-16
Advisory published
2026-08-22
Advisory updated
2026-10-16

Who should care

Linux system administrators and security teams should prioritize verifying the integrity of their kernel versions and applying patches to mitigate this vulnerability. They should also review compensating controls for exposed systems while remediation is scheduled and verified, and check relevant monitoring, detection, and logs for exposed assets that need extra review.

Why it matters

Linux system administrators and security teams should prioritize verifying the integrity of their kernel versions and applying patches to mitigate this vulnerability.

  • Incorrect identification of huge zero folios as ordinary THP folios
  • Splitting of huge zero folios and incorrect treatment

Technical summary

The vulnerability is caused by a subtle race condition in the reference-counted huge_zero_folio implementation. The fast path atomic logic fails to account for the fact that the shrinker can overwrite huge_zero_pfn with the ~0UL sentinel value after a racing get_huge_zero_folio installed a valid value there. This results in huge_zero_folio being correctly set but huge_zero_pfn being set incorrectly and thus is_huge_zero_pfn() and consequently is_huge_zero_pmd() will misidentify the huge zero folio as being an ordinary THP folio. This can result in the huge zero folio being split and otherwise treated incorrectly. The solution to this is very subtle as there is an atomic fast path, and thus ordering in weakly

Defensive priority

Linux system administrators and security teams should prioritize verifying the integrity of their kernel versions and applying patches to mitigate this vulnerability.

Recommended defensive actions

  • Verify kernel versions and apply patches
  • Monitor system logs for suspicious activity
  • Implement additional security measures to prevent exploitation
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented.
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The vulnerability is caused by a subtle race condition in the reference-counted huge_zero_folio implementation. The fast path atomic logic fails to account for the fact that the shrinker can overwrite huge_zero_pfn with the ~0UL sentinel value after a racing get_huge_zero_folio installed a valid value there.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-74632 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-74632

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-74632 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-74632

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • mm/huge_memory: fix huge_zero_pfn race

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/74xxx/CVE-2026-74632.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9c0fd1802ce06d7709f0bae4edeb085288f28764

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/b7041ba61c5da4e0b56f9be58cfb87d7689724e4

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9332b080ad57650d1dc582e54517f9fc78ef89cc

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/f3a874a903053c53fb53ba287ea9eacda69c68e8

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/6024f6d0d9b9ca5138bfc4ac6f6e4bdf616e42b3

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/105d04edbec83010df5728f74d17fd9c108e7553

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/ab7e4b407c7f58d1a003134eff3841f303d5ccc2

    Supplemental source

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.