fhandle: reject detached mounts in capable_wrt_mount()

{
  "id": "2c95b7794be7e39f0524db499461a50804a7fff89d4005be66b5616c528d0f5d",
  "url": "https://osv.dev/vulnerability/CVE-2026-72034",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "fhandle: reject detached mounts in capable_wrt_mount()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: fhandle: reject detached mounts in capable_wrt_mount() The recent fhandle RCU fix moved the mount namespace capability check into capable_wrt_mount(), so a non-NULL mnt_namespace survives the ns_capable() dereference. The helper still assumes the later READ_ONCE(mount->mnt_ns) must be non-NULL because may_decode_fh() checked is_mounted() first. That assumption is not stable. A detached mount from open_tree(..., OPEN_TREE_CLONE) can be dissolved on fput while open_by_handle_at() is between those checks, and umount_tree() can clear mount->mnt_ns. If the helper observes NULL, it dereferences mnt_ns->user_ns and panics. Return false when the RCU read observes a detached mount. This keeps the relaxed permission path conservative: a mount no longer attached to a namespace cannot authorize open_by_handle_at() access.",
    "evidence": "osv:CVE-2026-72034",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.97",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.40",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-72034",
      "aliases": [
        "CVE-2026-72034"
      ],
      "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": [
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                  "introduced": "620c266f394932e5decc4b34683a75dfc59dc2f4"
                },
                {
                  "fixed": "15104234c267ebe04b9f9a73e5c2179cc265ff60"
                },
                {
                  "fixed": "6c52226072a3c61337b1eec1799bb987748884fa"
                },
                {
                  "fixed": "6ee183d89261bf1d1cf9f06d80a40dab8f36ee55"
                },
                {
                  "fixed": "6c732471740bc2ac9b0946134f9f551dc75f4369"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72034.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.11.0"
                },
                {
                  "fixed": "6.12.97"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.40"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.5"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72034.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.095668588Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/15104234c267ebe04b9f9a73e5c2179cc265ff60",
        "https://git.kernel.org/stable/c/6c52226072a3c61337b1eec1799bb987748884fa",
        "https://git.kernel.org/stable/c/6c732471740bc2ac9b0946134f9f551dc75f4369",
        "https://git.kernel.org/stable/c/6ee183d89261bf1d1cf9f06d80a40dab8f36ee55",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72034.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-72034",
        "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/2026/72xxx/CVE-2026-72034.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-72034",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 497217,
  "published_at": "2026-08-15T05:51:55.739+00:00"
}