{"id":"CVE-2026-64295","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-64295","generatedAt":"2026-10-28T03:29:42.529Z","title":"In the Linux kernel, the following vulnerability has been resolved: mm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access The page_ext iteration API does not validate if the PFN still belongs to a valid section while…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access\n\nThe page_ext iteration API does not validate if the PFN still belongs to a\nvalid section while advancing the iterator.  When dynamically adding\nmemory in the hotplug path, it can lead to a NULL pointer dereference\nduring page_ext_lookup at the boundary of the last valid section when\niterator count equals __pgcount.\n\nThe for_each_page_ext() macro calls page_ext_iter_next() as its loop\nincrement.  for_each_page_ext() does a \"__page_ext =\npage_ext_iter_next(&__iter)\" at the end.  This causes page_ext_iter_next()\nto increment iter->index past __pgcount and call page_ext_lookup(start_pfn\n+ __pgcount).  During memory hotplug (online), the PFN at start_pfn +\n__pgcount may belong to a section that has not yet been initialized,\ncausing page_ext_lookup() to trigger a NULL pointer dereference.\n\n[   14.555124][  T846] Call trace:\n[   14.555125][  T846]  lookup_page_ext+0x6c/0x108 (P)\n[   14.555127][  T846]  page_ext_lookup+0x30/0x3c\n[   14.555129][  T846]  __reset_page_owner+0x11c/0x260\n[   14.571201][  T846]  __free_pages_ok+0x5e8/0x8e0\n[   14.571204][  T846]  __free_pages_core+0x78/0xf0\n[   14.571206][  T846]  generic_online_page+0x14/0x24\n[   14.597782][  T846]  online_pages+0x178/0x30c\n[   14.597784][  T846]  memory_block_change_state+0x284/0x32c\n[   14.597787][  T846]  memory_subsys_online+0x4c/0x64\n[   14.597789][  T846]  device_online+0x88/0xb0\n[   14.597791][  T846]  online_memory_block+0x30/0x40\n[   14.597793][  T846]  walk_memory_blocks+0xac/0xe8\n[   14.597794][  T846]  add_memory_resource+0x280/0x298\n[   14.656161][  T846]  add_memory+0x60/0x98\n\nMove the iteration boundary enforcement inside the iterator functions, so\ncallers cannot inadvertently access beyond the requested range.","published":"2026-07-25T10:17:10.000Z","lastModified":"2026-08-17T05:17:29.000Z","status":"Analyzed","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-476"],"affected":["linux/linux kernel"],"epss":{"score":0.0016,"percentile":0.05145,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.16%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/377b1cd6bbcf327338cd951cc2fd74bc75540235","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8dcaa0f87a88d720d13106f3a306c6b61d189d86","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ffd017237cfe99e6e5602ab14179b0e6878a0840","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-64295","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}