{
  "cveId": "CVE-2026-98993",
  "url": "https://patchblox.com/security/cve/CVE-2026-98993",
  "summary": "CVE-2026-98993 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-98993, released October 24, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "namespace: don\u0027t inherit MNT_UMOUNT in clone_mnt()",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  namespace: don\u0027t inherit MNT_UMOUNT in clone_mnt()  MNT_UMOUNT gets raised on a mount that umount_tree() or umount_one() has taken out of its namespace. It\u0027s never cleared. __detach_mounts() unhooks a mount that carries it instead of unmounting it.  disconnect_mount() lets an unmounted child stay attached only if its parent carries it. propagate_umount() takes it as the sign that a mount is going to be unmounted when it decides what else can be unmounted, where a chain of locked mounts ends and where a for reparenting an overmount.  clone_mnt() copies the flags of the source and only masks MNT_INTERNAL_FLAGS which doesn\u0027t include MNT_UMOUNT. A mount that was lazily unmounted but is kept alive by a file descriptor can still be copied when its root is an nsfs or pidfs file because may_copy_tree() accepts those before checking whether the source is mounted at all:    mount --bind /proc/self/ns/net /tmp/x   exec 3\u003C /tmp/x   umount -l /tmp/x   mount --bind /proc/self/fd/3 /tmp/y  The mount on /tmp/y is attached to the caller\u0027s namespace with MNT_UMOUNT already set and every copy of it inherits the flag again.  That causes a number of bugs:  - Unlink its mountpoint from a mount namespace where it isn\u0027t one.   __detach_mounts() takes it for a mount that was unmounted earlier,   unhooks it from its parent and drops the reference the namespace   holds on it. It stays in the namespace with one reference too few   and as its own parent, so it can\u0027t be unmounted through the file   descriptor anymore and the namespace never finds it again. When the   namespace goes away it\u0027s leaked and points to a freed struct   mnt_namespace that may_change_propagation() and anon_ns_root() read   on the next propagation change or mount_setattr() through the file   descriptor.  - Make it shared and unmount a peer. trace_transfers() follows the   flag from the peer into it and strips it from its peer group.  - Let a propagated umount reach it. gather_candidates() marks it with   T_UMOUNT_CANDIDATE but never puts it on the candidate list, so the   mark is never cleared and every later propagated umount skips it. If   it\u0027s the parent of a locked mount handle_locked() takes it as the   cutoff and commits the locked child that should have stayed and   disconnect_mount() leaves that child attached to it, unmounted under   a mounted parent, which is what disconnect_mount() exists to   prevent. When the namespace goes away umount_tree() visits the child   a second time. And once __detach_mounts() has made it its own parent   reparent() never finds the end of the chain of unmounted parents.  A clone is a new mount that has never been unmounted. Add MNT_UMOUNT to MNT_INTERNAL_FLAGS so clone_mnt() never copies it. And warn when umount_tree() reaches a mount that already has it set.",
  "published": "2026-10-23T13:17:21Z",
  "severity": "Moderate",
  "cvss": 7.8,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
  "epss": 0.00176,
  "epssPercentile": 0.07144,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98993",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.115-2",
      "fix": "DEBIAN-CVE-2026-98993",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98993",
      "released": "2026-10-24T13:25:57Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.11-1",
      "fix": "DEBIAN-CVE-2026-98993",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98993",
      "released": "2026-10-24T13:25:57Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T06:59:42Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}