{"cve":"CVE-2026-64514","nvd":{"published":"2026-07-25T10:17:37.633","modified":"2026-08-17T05:17:57.617","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nuserfaultfd: gate must_wait writability check on pte_present()\n\nuserfaultfd_must_wait() and userfaultfd_huge_must_wait() read the PTE\nwithout taking the page table lock and then apply pte_write() /\nhuge_pte_write() to it.  Those accessors decode bits from the present\nencoding only; on a swap or migration entry they read the offset bits that\nhappen to share the same position and return an undefined result.\n\nThe intent of the check is \"is this fault still WP-blocked?\".  A\nnon-marker swap entry means the page is in transit -- the userfault\ncontext the original fault delivered against is no longer the same, and\nthe swap-in or migration completion path will re-deliver a fresh fault if\nuserspace still needs to handle it.  Worst case under the current code the\ngarbage write bit says \"wait\", and the thread stays asleep until a\nUFFDIO_WAKE that may never arrive.\n\nGate the writability check on pte_present() so the lockless re-check only\ninspects present-PTE bits when the entry is actually present.  The\nnon-present, non-marker case returns \"don't wait\" and lets the fault path\nretry.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0","https://git.kernel.org/stable/c/5f4dbdb0a87596214076b20b94f2b71b522170b3","https://git.kernel.org/stable/c/60d696a037eeeedfb57756dfe7ec08a1587c8631","https://git.kernel.org/stable/c/710183888174639a15fcec16cd1af766b8480bb7","https://git.kernel.org/stable/c/8e80af52db652fbc41320eee45a4f73bc029faf2"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:46:40.600842820+00:00"},"epss":{"cve":"CVE-2026-64514","score":0.00177,"percentile":0.07286,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}