filelock: ReadWriteLock on the hard-link route deletes any directory another user renames onto its .filelock-* link directory name

{
  "id": "53fa87a339deae9e6b8ae0aa1260705eab2cddbbffcd71b1431d791faa14339d",
  "url": "https://osv.dev/vulnerability/CVE-2026-112937",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "filelock: ReadWriteLock on the hard-link route deletes any directory another user renames onto its .filelock-* link directory name",
    "summary": "filelock is a platform-independent file lock for Python. From 4.1.0 until 4.2.1, ReadWriteLock can remove a randomized .filelock-* private-hard-link directory during cleanup, allowing another local user with rename access in a non-sticky parent to observe a live name or forge a dead-owner sweep name and rename a sibling directory onto it for deletion. This issue is fixed in version 4.2.1.",
    "evidence": "osv:CVE-2026-112937",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-112937",
      "aliases": [
        "CVE-2026-112937",
        "GHSA-jqc4-5cvw-7w85"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/tox-dev/filelock",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6c0ecc28f898f08cd0438cd489c3eaabad79a4b7"
                },
                {
                  "fixed": "60331bb89f325020b48bc51bde904c6446384e4a"
                },
                {
                  "fixed": "5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:tox-dev:filelock:*:*:*:*:*:python:*:*",
                    "range": [
                      {
                        "introduced": "4.1.0"
                      },
                      {
                        "fixed": "4.2.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "60331bb89f325020b48bc51bde904c6446384e4a"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "4.2.1"
                  }
                ]
              }
            }
          ],
          "versions": [
            "4.2.0",
            "4.1.2",
            "4.1.1",
            "4.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-112937.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.017395445Z",
      "provider": "osv",
      "references": [
        "https://github.com/tox-dev/filelock/releases/tag/4.2.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/112xxx/CVE-2026-112937.json",
        "https://github.com/tox-dev/filelock/security/advisories/GHSA-jqc4-5cvw-7w85",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-112937",
        "https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d",
        "https://github.com/tox-dev/filelock/pull/834"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-367"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/112xxx/CVE-2026-112937.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-112937",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518576,
  "published_at": "2026-10-20T14:36:28.129+00:00"
}