CVE-2026-80893mm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork()

Description

In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork() copy_hugetlb_page_range() clears the uffd-wp bit of migration and hwpoison entries with huge_pte_clear_uffd_wp(), which operates on the present-PTE bit position. Swap entries keep the uffd-wp state elsewhere -- the migration branch reads and sets it with pte_swp_uffd_wp() and pte_swp_mkuffd_wp() -- and the present-PTE position falls into the swap payload. On x86-64 it lands in the inverted swap offset, where a naturally-aligned hugetlb PFN always has the affected bit set, so the clear advances the encoded PFN by two pages. No userfaultfd needs to be involved: the clear is guarded only by the child VMA not being uffd-wp registered, so a plain fork() with an in-flight hugetlb migration entry (or a poisoned hugetlb page) corrupts the entry copied into the child. Instrumenting the clear and forking after MADV_HWPOISON on a 2MB anon hugetlb page shows: offset before=120e00 offset after =120e02 The fallout is mostly latent: rmap walks match migration entries by folio range and remove_migration_pte() rebuilds the PTE from the folio, so a within-folio PFN skew heals once migration completes. But any path that re-encodes the corrupted offset -- e.g. hugetlb_change_protection() rewriting a writable migration entry via make_readable_migration_entry(swp_offset(entry)) -- propagates it. Migration entries legitimately carry uffd-wp, so clear it with pte_swp_clear_uffd_wp(), matching copy_nonpresent_pte() and move_huge_pte(). A hwpoison entry, on the other hand, never carries the uffd-wp bit: it is installed fresh by make_hwpoison_entry() (try_to_unmap_one() does not preserve uffd-wp on the hwpoison path) and hugetlb_change_protection() leaves hwpoison entries untouched. There was nothing to clear there, only the corruption, so drop the clear entirely.

Timeline

Scores

No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.

EPSS (exploitation in 30 days)

0.17% · top 93% of all CVEs (13 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.

Affected products

• Linux · Linux

  • affected bc70fbf269fdff410b0b6d75c3770b9f59117b90 – < f1b1311c0352873137768bac5a126e491271a747
  • affected bc70fbf269fdff410b0b6d75c3770b9f59117b90 – < 69cb5825d9988c7944bc9f1dc08cb233655405a7
  • affected bc70fbf269fdff410b0b6d75c3770b9f59117b90 – < 8b0de7005b148738d79d6c45594d566489948a68
  • affected bc70fbf269fdff410b0b6d75c3770b9f59117b90 – < 2b9a07002c2f296aa6a9c591213933d3492e3089
  • affected bc70fbf269fdff410b0b6d75c3770b9f59117b90 – < 2fa11c60c9c06bafc19cf4d9efdaa36a38079e87
  • affected bc70fbf269fdff410b0b6d75c3770b9f59117b90 – < 83abe2fd5b3aeb3123b5408a5a91709c5538fb23

• Linux · Linux

  • affected 5.19
  • unaffected < 5.19
  • unaffected 6.1.183 – ≤ 6.1.*
  • unaffected 6.6.151 – ≤ 6.6.*
  • unaffected 6.12.103 – ≤ 6.12.*
  • unaffected 6.18.44 – ≤ 6.18.*
  • unaffected 7.1.8 – ≤ 7.1.*
  • unaffected 7.2 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-71643 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-80893](https://cveledger.app/badge/CVE-2026-80893.svg)](https://cveledger.app/cve/CVE-2026-80893)

Record last updated 6 Nov 2026, 17:05 UTC.