namespace: reset the old parent's ->overmount in mnt_change_mountpoint()

{
  "id": "66e1db636f5ab79c0b2fa20977af6d89e421a313b2c3005b705675f1001ed511",
  "url": "https://osv.dev/vulnerability/CVE-2026-98995",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "namespace: reset the old parent's ->overmount in mnt_change_mountpoint()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: namespace: reset the old parent's ->overmount in mnt_change_mountpoint() __umount_mnt() resets ->overmount of the parent when it unmounts the mount that overmounts it. mnt_change_mountpoint() doesn't. It moves the mount to its new parent and leaves the old one pointing at it. For a mount that is moved beneath in attach_recursive_mnt() that doesn't matter. The new mount has already reset ->overmount of the old parent by the time the old top mount is moved onto it. It matters for reparent() though. propagate_umount() moves a surviving overmount onto the first ancestor that isn't going to be unmounted. The mount it was taken from is unmounted immediately afterwards. If a file descriptor keeps that unmounted mount alive ->overmount points at the moved mount. That's a dangling pointer and UAF as the moved mount is unmounted and freed. do_lock_mount() follows ->overmount from the target path under mount_lock. With a file descriptor on such a mount as the target of a mount beneath topmost_overmount() walks into the freed mount and do_lock_mount() takes references on whatever it finds there. So reset ->overmount of the old parent in mnt_change_mountpoint() the same way __umount_mnt() does. A mount's ->overmount is then always a mount that is attached to it.",
    "evidence": "osv:CVE-2026-98995",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.57",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.11",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-98995",
      "aliases": [
        "CVE-2026-98995"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "ffdc52fbbd5835a936ad683c943d6d103a2d4514"
                },
                {
                  "fixed": "5e0a1f2c753a79749bc2ead3ae2f2ede3941daa5"
                },
                {
                  "fixed": "08d575ee89393fd812dbdca7b5d7b4574cd5a564"
                },
                {
                  "fixed": "476ef286a7a5db8bda51325dc0c45887b4d99d9a"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98995.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.17.0"
                },
                {
                  "fixed": "6.18.57"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.11"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98995.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:40.151123651Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/08d575ee89393fd812dbdca7b5d7b4574cd5a564",
        "https://git.kernel.org/stable/c/476ef286a7a5db8bda51325dc0c45887b4d99d9a",
        "https://git.kernel.org/stable/c/5e0a1f2c753a79749bc2ead3ae2f2ede3941daa5",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98995.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98995",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98995.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98995",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 507773,
  "published_at": "2026-10-23T12:20:14.155+00:00"
}