{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "bf630c40164162ba1d3933c2f5e3397d083e0948"
            },
            {
              "fixed": "acbe9e4418e2ef7bef1a12e62e0e7d6145a15190"
            },
            {
              "fixed": "702ff3fe499876e09c45558a05366d21a5bc41ab"
            },
            {
              "fixed": "bd2feb7796b6585938a4241e7b7c4148a6f7b762"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.15.0"
            },
            {
              "fixed": "6.18.57"
            }
          ],
          "type": "ECOSYSTEM"
        },
        {
          "events": [
            {
              "introduced": "6.19.0"
            },
            {
              "fixed": "7.2.11"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98991.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: queue a mount only once for mount notifications\n\nmnt_notify_add() puts a mount on notify_list. It doesn't check whether\nthe mount is on the list already. That's fine as long as every mount is\nqueued at most once per namespace_sem hold. It isn't.\n\npropagate_umount() moves a surviving overmount off a stack of mounts\nthat are going away and queues it as moved. shrink_submounts() and\nmark_mounts_for_expiry() call umount_tree() for several mounts under a\nsingle namespace_sem hold. So the second umount_tree() can take down\nexactly the mount the first one reparented, reparent it once more and so\nend up queueing it a second time.\n\nThe second list_add_tail() cuts the mounts queued in between out of the\nlist while the head still points at the last of them. notify_mnt_list()\nthen only visits that one mount and the others are freed after the grace\nperiod with notify_list still pointing at them. Every later mount\noperation on the host walks freed memory:\n\n  BUG: KASAN: slab-use-after-free in __list_add_valid_or_report\n  Read of size 8 at addr ffff8881003d57e0 by task notify_dq/162\n   __list_add_valid_or_report+0x15c/0x1a0\n   mnt_add_to_ns+0x322/0x890\n   attach_recursive_mnt.isra.0+0xf2a/0x1a00\n   path_mount+0x139c/0x1d40\n\nThis needs a mount with MNT_SHRINKABLE to bind from. That's what\nfinish_automount() creates (submounts of NFS, AFS and CIFS and the\ntracefs mount below debugfs). Bind mounts inherit the flag. A mount\nnamespace with a FAN_MARK_MNTNS mark does the rest and root in a user\nnamespace can have both.\n\nInitialize to_notify in alloc_vfsmnt() and leave a mount alone that is\nqueued already. mnt_notify() looks at the state the mount has when the\nlist is drained so a single entry per mount is enough. The move event\nfor a mount that is unmounted under the same hold is lost. That's fine.\nThe detach is what matters.",
  "id": "CVE-2026-98991",
  "modified": "2026-10-28T02:30:46.206168372Z",
  "published": "2026-10-23T12:20:10.289Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/702ff3fe499876e09c45558a05366d21a5bc41ab"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/acbe9e4418e2ef7bef1a12e62e0e7d6145a15190"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/bd2feb7796b6585938a4241e7b7c4148a6f7b762"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98991.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98991"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "namespace: queue a mount only once for mount notifications"
}