{
  "cveId": "CVE-2026-63950",
  "url": "https://patchblox.com/security/cve/CVE-2026-63950",
  "summary": "CVE-2026-63950 is fixed in 20 products on 1 platform, first by ALAS2023-2026-1881, released June 22, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  mm/rmap: initialize nr_pages to 1 at loop start...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  mm/rmap: initialize nr_pages to 1 at loop start in try_to_unmap_one  Initialize nr_pages to 1 at the start of each loop iteration, like folio_referenced_one() does.  Without this, nr_pages computed by a previous folio_unmap_pte_batch() call can be reused on a later iteration that does not run folio_unmap_pte_batch() again.  mmap a 64K large folio with MAP_ANONYMOUS | MAP_DROPPABLE, then call madvise(MADV_FREE), then make the last page device-exclusive via HMM_DMIRROR_EXCLUSIVE.  Trigger node reclaim through sysfs.  Now, in try_to_unmap_one(), we will first clear the first 15 out of 16 entries mapping the lazyfree folio.  This will set nr_pages to 15.  In the next pvmw walk, this nr_pages gets reused on a device-exclusive pte, thus potentially corrupting folio refcount/mapcount.  At the moment, I have a userspace program which can make the kernel spit out a trace, but the blow up is in folio_referenced_one(), because there are existing bugs in the interaction between device-private and rmap (which too I am investigating).  I did a one liner kernel change to avoid going into folio_referenced_one(), and the kernel blows up at folio_remove_rmap_ptes in try_to_unmap_one which is what I wanted.  Note that the bug is there not since file folio batching but lazyfree folio batching, since device-exclusive only works for anonymous folios.  Userspace visible effect is simply kernel crashing somewhere due to refcount/mapcount corruption.",
  "published": "2026-06-22T09:00:00Z",
  "severity": "high",
  "cvss": 7.8,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
  "epss": 0.00173,
  "epssPercentile": 0.06834,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "bpftool6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "bpftool6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel-livepatch-6.18.35-68.127",
      "release": "amzn 2023",
      "fixedVersion": "1:1.0-0.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo-common-aarch64",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-debuginfo-common-x86_64",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-devel",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-headers",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-modules-extra",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-modules-extra-common",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "kernel6.18-tools-devel",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.0.12-1",
      "fix": "DEBIAN-CVE-2026-63950",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-63950",
      "released": "2026-07-20T12:58:36Z"
    },
    {
      "platform": "linux",
      "product": "microvm-kernel6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "perf6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "perf6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-perf6.18",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    },
    {
      "platform": "linux",
      "product": "python3-perf6.18-debuginfo",
      "release": "amzn 2023",
      "fixedVersion": "1:6.18.35-68.127.amzn2023",
      "fix": "ALAS2023-2026-1881",
      "url": "https://patchblox.com/security/fix/linux/alas2023-2026-1881",
      "released": "2026-06-22T09:00:00Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-10T20:03:11Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}