filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion

{
  "id": "83553c4860216146054f639aed8f73799eb6b173284f5281b2fe89adab43eaeb",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-112911",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion",
    "summary": "filelock is a platform-independent file lock for Python. From 3.30.0 until 4.2.1, StrictSoftFileLock versions from 3.30.0 and SoftReadWriteLock versions from 4.0.0 can adopt a protocol directory created first by another local user in a shared parent directory, allowing that user to alter protocol state and admit concurrent holders. This issue is fixed in version 4.2.1.",
    "evidence": "cve:CVE-2026-112911",
    "products": [
      {
        "name": {
          "value": "filelock",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-112911",
      "aliases": [
        "CVE-2026-112911"
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "scope": "UNCHANGED",
            "version": "3.1",
            "baseScore": 6.3,
            "attackVector": "LOCAL",
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H",
            "integrityImpact": "HIGH",
            "userInteraction": "NONE",
            "attackComplexity": "HIGH",
            "availabilityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "confidentialityImpact": "NONE"
          }
        }
      ],
      "affected": [
        {
          "vendor": "tox-dev",
          "product": "filelock",
          "versions": [
            {
              "status": "affected",
              "version": ">= 3.30.0, < 4.2.1"
            }
          ]
        }
      ],
      "modified": "2026-10-28T15:09:43.507Z",
      "provider": "cve",
      "references": [
        "https://github.com/tox-dev/filelock/security/advisories/GHSA-9c4x-gm8v-wgc4",
        "https://github.com/tox-dev/filelock/pull/839",
        "https://github.com/tox-dev/filelock/commit/bfa066d65a1ba9106f86ee9d027f7588b9c77e03",
        "https://github.com/tox-dev/filelock/releases/tag/4.2.1"
      ],
      "provider_metadata": {
        "adp": [
          {
            "title": "CISA ADP Vulnrichment",
            "metrics": [
              {
                "other": {
                  "type": "ssvc",
                  "content": {
                    "id": "CVE-2026-112911",
                    "role": "CISA Coordinator",
                    "options": [
                      {
                        "Exploitation": "poc"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "version": "2.0.3",
                    "timestamp": "2026-10-28T15:09:37.663560Z"
                  }
                }
              }
            ],
            "references": [
              {
                "url": "https://github.com/tox-dev/filelock/security/advisories/GHSA-9c4x-gm8v-wgc4",
                "tags": [
                  "exploit"
                ]
              }
            ],
            "providerMetadata": {
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP",
              "dateUpdated": "2026-10-28T15:09:43.507Z"
            }
          }
        ],
        "cna": {
          "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
          "shortName": "GitHub_M",
          "dateUpdated": "2026-10-20T14:21:24.480Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-112911",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 454314,
  "published_at": "2026-10-20T14:21:24.48+00:00"
}