open_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE

{
  "id": "b9825e9d42056b2209b7c370d04ee83e8c1de746546d23d702784884ecf047da",
  "url": "https://osv.dev/vulnerability/CVE-2025-39717",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "open_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: open_tree_attr: do not allow id-mapping changes without OPEN_TREE_CLONE As described in commit 7a54947e727b ('Merge patch series \"fs: allow changing idmappings\"'), open_tree_attr(2) was necessary in order to allow for a detached mount to be created and have its idmappings changed without the risk of any racing threads operating on it. For this reason, mount_setattr(2) still does not allow for id-mappings to be changed. However, there was a bug in commit 2462651ffa76 (\"fs: allow changing idmappings\") which allowed users to bypass this restriction by calling open_tree_attr(2) *without* OPEN_TREE_CLONE. can_idmap_mount() prevented this bug from allowing an attached mountpoint's id-mapping from being modified (thanks to an is_anon_ns() check), but this still allows for detached (but visible) mounts to have their be id-mapping changed. This risks the same UAF and locking issues as described in the merge commit, and was likely unintentional.",
    "evidence": "osv:CVE-2025-39717",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.16.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-39717",
      "aliases": [
        "CVE-2025-39717"
      ],
      "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": "2462651ffa76b87f9c2e4403ef6e6b89b703fb2f"
                },
                {
                  "fixed": "69dbdc711d9130136824e3830191a6afffa0a1f0"
                },
                {
                  "fixed": "9308366f062129d52e0ee3f7a019f7dd41db33df"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39717.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.15.0"
                },
                {
                  "fixed": "6.16.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39717.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.987645738Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/69dbdc711d9130136824e3830191a6afffa0a1f0",
        "https://git.kernel.org/stable/c/9308366f062129d52e0ee3f7a019f7dd41db33df",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39717.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-39717",
        "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/2025/39xxx/CVE-2025-39717.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-39717",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521888,
  "published_at": "2025-09-05T17:21:24.528+00:00"
}