{"id":"CVE-2026-64514","title":"userfaultfd: gate must_wait writability check on pte_present()","summary":"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…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 369cd2121be440543280b91056de187f625d0dbb < a5700a4c1c9099ac2ac73fe8a09cf059972e0d2f","Linux >= 369cd2121be440543280b91056de187f625d0dbb < d4026417e8184d13850a0bad4d96ceb6ed9f7152","Linux >= 369cd2121be440543280b91056de187f625d0dbb < 29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0","Linux >= 369cd2121be440543280b91056de187f625d0dbb < 5f4dbdb0a87596214076b20b94f2b71b522170b3","Linux >= 369cd2121be440543280b91056de187f625d0dbb < a6e9a4939e359599701b1da351e84f72e021443a","Linux >= 369cd2121be440543280b91056de187f625d0dbb < 60d696a037eeeedfb57756dfe7ec08a1587c8631","Linux >= 369cd2121be440543280b91056de187f625d0dbb < 710183888174639a15fcec16cd1af766b8480bb7","Linux >= 369cd2121be440543280b91056de187f625d0dbb < 8e80af52db652fbc41320eee45a4f73bc029faf2","Linux 4.11"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-11-06T16:40:57.422475Z"},"published":"2026-07-25","updated":"2026-11-06","sourceUpdated":"2026-11-06T16:44:56.292Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64514","references":[{"url":"https://git.kernel.org/stable/c/a5700a4c1c9099ac2ac73fe8a09cf059972e0d2f"},{"url":"https://git.kernel.org/stable/c/d4026417e8184d13850a0bad4d96ceb6ed9f7152"},{"url":"https://git.kernel.org/stable/c/29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0"},{"url":"https://git.kernel.org/stable/c/5f4dbdb0a87596214076b20b94f2b71b522170b3"},{"url":"https://git.kernel.org/stable/c/a6e9a4939e359599701b1da351e84f72e021443a"},{"url":"https://git.kernel.org/stable/c/60d696a037eeeedfb57756dfe7ec08a1587c8631"},{"url":"https://git.kernel.org/stable/c/710183888174639a15fcec16cd1af766b8480bb7"},{"url":"https://git.kernel.org/stable/c/8e80af52db652fbc41320eee45a4f73bc029faf2"}],"tags":["cve.org"],"epss":0.00177,"epssPercentile":0.0733,"ingestedAt":"2026-11-06T16:57:43.156Z","slug":"CVE-2026-64514","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < a5700a4c1c9099ac2ac73fe8a09cf059972e0d2f`\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < d4026417e8184d13850a0bad4d96ceb6ed9f7152`\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < 29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0`\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < 5f4dbdb0a87596214076b20b94f2b71b522170b3`\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < a6e9a4939e359599701b1da351e84f72e021443a`\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < 60d696a037eeeedfb57756dfe7ec08a1587c8631`\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < 710183888174639a15fcec16cd1af766b8480bb7`\n- `Linux >= 369cd2121be440543280b91056de187f625d0dbb < 8e80af52db652fbc41320eee45a4f73bc029faf2`\n- `Linux 4.11`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}