# CVE-2026-112907: filelock: On Windows an oplock on a soft lock's marker holds SoftFileLock.acquire() past its timeout and blocks the stale break

Status: published. Published: 2026-11-05. Updated: 2026-11-05.

filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, soft lock classes on Windows read an existing marker with _read_lock_file and remove a stale marker through break_lock_file using pathname operations that wait for an oplock break. Another local account with read access to an unheld marker can keep a Level 1 or batch oplock unanswered, causing SoftFileLock.acquire and related async or fallback locks to wait beyond timeout, blocking=False, and cancel_check. A stale marker under the oplock cannot be broken, but mutual exclusion remains intact and no file other than the marker is accessed. This issue is fixed in version 4.2.1.

## Remediation

- fix: filelock (PyPI): OSV reports a fixed version 4.2.1. Check the advisory for supported release branches. (source: OSV GHSA-567q-5qvw-pf92) — https://github.com/advisories/GHSA-567q-5qvw-pf92

## Affected products and versions

- tox-dev / filelock: >= 3.22.0, < 4.2.1 (affected). Source: CNA: GitHub_M
-  / filelock (filelock): 3.22.0 (affected, PyPI); 3.23.0 (affected, PyPI); 3.24.0 (affected, PyPI); 3.24.1 (affected, PyPI); 3.24.2 (affected, PyPI); 3.24.3 (affected, PyPI); 3.25.0 (affected, PyPI); 3.25.1 (affected, PyPI); 3.25.2 (affected, PyPI); 3.28.0 (affected, PyPI); 3.29.0 (affected, PyPI); 3.29.1 (affected, PyPI); 3.29.2 (affected, PyPI); 3.29.3 (affected, PyPI); 3.29.4 (affected, PyPI); 3.29.5 (affected, PyPI); 3.29.6 (affected, PyPI); 3.29.7 (affected, PyPI); 3.30.0 (affected, PyPI); 3.30.1 (affected, PyPI); 3.30.2 (affected, PyPI); 3.30.3 (affected, PyPI); 3.31.0 (affected, PyPI); 3.31.1 (affected, PyPI); 3.31.2 (affected, PyPI); 3.32.0 (affected, PyPI); 3.32.2 (affected, PyPI); 3.32.3 (affected, PyPI); 3.32.4 (affected, PyPI); 3.32.5 (affected, PyPI); 3.32.6 (affected, PyPI); 3.32.7 (affected, PyPI); 4.0.0 (affected, PyPI); 4.0.1 (affected, PyPI); 4.0.10 (affected, PyPI); 4.0.11 (affected, PyPI); 4.0.12 (affected, PyPI); 4.0.2 (affected, PyPI); 4.0.3 (affected, PyPI); 4.0.4 (affected, PyPI); 4.0.5 (affected, PyPI); 4.0.6 (affected, PyPI); 4.0.7 (affected, PyPI); 4.0.8 (affected, PyPI); 4.0.9 (affected, PyPI); 4.1.0 (affected, PyPI); 4.1.1 (affected, PyPI); 4.1.2 (affected, PyPI); 4.2.0 (affected, PyPI); Ecosystem version events: introduced 3.22.0; fixed 4.2.1. Source: OSV GHSA-567q-5qvw-pf92

## Severity and prioritization

- CVSS 3.1: 2.5 (low); CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-667

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/tox-dev/filelock/security/advisories/GHSA-567q-5qvw-pf92 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/tox-dev/filelock/pull/835 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tox-dev/filelock/commit/97d694a9a3ee1721d6c79a480174dfd9b060a080 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tox-dev/filelock/commit/e1e825b1992f69fb6b346dc395d5ae4893536c0a (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/tox-dev/filelock/releases/tag/4.2.1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/advisories/GHSA-567q-5qvw-pf92 (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-567q-5qvw-pf92 (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-112907; retrieved 2026-11-05; source updated 2026-11-05

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-567q-5qvw-pf92; retrieved 2026-11-05; source updated 2026-10-23

Revision: c3c7f4d763ccb1123e711b5c7fb34b9135de5654a842f9fb6a92e5f062b55e1a

Canonical: https://y2.dev/cve/CVE-2026-112907

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.