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Response snapshot Oct 27, 2026, 03:07 UTC

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VulnerabilityCVE-2026-112913

filelock: ReadWriteLock on Windows acts on SQLite side files another local user places beside its database

On Windows, `ReadWriteLock` and `AsyncReadWriteLock` (the SQLite-backed reader/writer lock) connect SQLite to the lock database by its path, in every directory.

Published Updated

At a glance

Exploited
Not known
Severity
3.3 Low (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: filelock: 4.2.1. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-9vhv-jxww-xfm5 (opens a new tab)

What happened

On Windows, `ReadWriteLock` and `AsyncReadWriteLock` (the SQLite-backed reader/writer lock) connect SQLite to the lock database by its path, in every directory. SQLite derives three side files from that path: ` -journal`, the rollback journal (pages saved to undo an interrupted write); ` -wal`, the write-ahead log (changes kept outside the main file); and ` -shm`, the shared-memory index of the WAL.

SQLite acts on whichever of these it finds beside the database before the lock runs any statement. Another local account that can create files in the database's directory, but not delete files of other accounts there, places such a side file beside the database and denies everyone `DELETE` on it, which a file's creator may do.

`C:\Windows\Temp` (the temporary directory of services, granting `BUILTIN\Users` create but not delete) and `C:\Users\Public` are such directories.

With a `-wal` in place, every `read_lock()` and `write_lock()` of the user running the lock (below: the lock user) raises `sqlite3.OperationalError: disk I/O error` at once, whatever `timeout` says, until that account removes its file; the lock user cannot.

Continue reading

With a `-journal` beside a lock database that holds a table, SQLite replays the journal and deletes the file the journal names, a file of the lock user, and the acquire reports success. Affected versions are filelock 3.20.4 through 4.2.0 on Windows.

The maintainers found this while reviewing the fix for the POSIX form of the defect, GHSA-v4x8-3wr5-3wq8, whose text says "Windows does not take this path" (review round 4, finding F2 of set D). It is not among the findings of the report Anthropic's OSS Scanner sent on 15 October 2026.

## Severity

**CVSS 3.1 `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L` scores 3.3 (Low).**

`AV:L` (local): the other account needs a logon on the same host. `AC:L` (low attack complexity): create one file beside the database and set its ACL (access control list); no race, and the other account can place the file days earlier. `PR:L` (low privileges): an ordinary account that can create files in the directory is enough. `UI:N` (no user interaction). `S:U` (scope unchanged).

`C:N` (no confidentiality impact): the other account learns nothing. `I:N` (no integrity impact in the scored variant): see the scoring note. `A:L` (partial availability impact): every acquire fails with an exception that `Timeout` handlers do not catch, until the other account removes its file; no crash, and the lock's own data is not changed.

Scoring note. The deletion variant reads `CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L` (3.6): `I:L` because the lock user's process deletes one file the journal names, `AC:H` because it needs a lock database that holds a table, which filelock does not create, and a journal the lock user can open for writing.

The lower-reading rule of this advisory set scores the variant that reaches every `ReadWriteLock` on Windows in such a directory, 3.3, and describes the deletion variant under Mechanism. Classification from the review: **security** (another account), availability for the scored variant.

## Scope and preconditions

- Platform and classes: Windows only. `ReadWriteLock` and `AsyncReadWriteLock`, both of which connect through `_connect`. On Linux and macOS the lock takes other routes, covered by GHSA-v4x8-3wr5-3wq8. - Directory: one where another account can create files but cannot delete the lock user's.

`C:\Windows\Temp` carries `BUILTIN\Users:(CI)(S,WD,AD,X)` (create file and create subdirectory, no delete child); `C:\Users\Public` and any directory with such an entry qualify. A directory only the lock user can write, such as `%LOCALAPPDATA%` or the per-user temporary directory, is not affected. - The other account creates ` -wal`, grants everyone modify and denies everyone `DELETE` on it.

A file's creator may set both. The lock user can open and read the file but not delete it. - Deletion variant: the lock database holds at least one table (filelock creates an empty database, and the review's reproducer has the lock account create the table), and the other account's ` -journal` grants the lock account modify rights. The journal's tail names a file the lock user can delete.

- What the lock user sees: `write_lock(timeout=1)` raised `sqlite3.OperationalError: disk I/O error` with the undeletable `-wal` in place; with the writable journal the acquire succeeded and the named file was gone; with an undeletable journal every acquire raised `sqlite3.OperationalError: unable to open database file`.

- The documentation at the scanned commit states "the lock directory must not be writable by untrusted users" for `WindowsFileLock`, in its symlink paragraph; the `ReadWriteLock` documentation names no directory requirement on Windows.

## Affected code

Scanned commit `b831496b0273`: the [Windows branch of `_connect`](https://github.com/tox-dev/filelock/blob/b831496b0273ecd11bf02b8d080ca8b673a538c1/src/filelock/_read_write.py#L951-L965) checks the database through a handle and then calls `sqlite3.connect(database, ...)` with the path. [`_open_lock_database`](https://github.com/tox-dev/filelock/blob/b831496b0273ecd11bf02b8d080ca8b673a538c1/src/filelock/_read_write.

py#L1079-L1091) and [`_raise_if_wal`](https://github.com/tox-dev/filelock/blob/b831496b0273ecd11bf02b8d080ca8b673a538c1/src/filelock/_read_write.py#L1094-L1101) inspect that handle, not the side files. The first statement is [`PRAGMA busy_timeout=...; PRAGMA journal_mode=MEMORY;` at L816](https://github.com/tox-dev/filelock/blob/b831496b0273ecd11bf02b8d080ca8b673a538c1/src/filelock/_read_write.py#L816).

[`_do_acquire_inner` at L763](https://github.com/tox-dev/filelock/blob/b831496b0273ecd11bf02b8d080ca8b673a538c1/src/filelock/_read_write.py#L763) turns only `"database is locked"` into `Timeout`; any other `sqlite3.OperationalError` leaves the acquire.

## Introduced

[cfd4446](https://github.com/tox-dev/filelock/commit/cfd4446) "feat(lock): add SQLite-based ReadWriteLock" ([#399](h

Affected package ranges reported by GitHub: filelock: >= 3.20.4, <= 4.2.0

Scores and how they were measured

CVSS base severity

3.3

Version 3.1As of

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-9vhv-jxww-xfm5 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-9vhv-jxww-xfm5, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). filelock: ReadWriteLock on Windows acts on SQLite side files another local user places beside its database (CVE-2026-112913). https://kevwire.com/record/CVE-2026-112913

MLA

"filelock: ReadWriteLock on Windows acts on SQLite side files another local user places beside its database (CVE-2026-112913)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-112913.

Chicago

KEVWire. "filelock: ReadWriteLock on Windows acts on SQLite side files another local user places beside its database (CVE-2026-112913)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-112913.

Evidence summary (plain text)

filelock: ReadWriteLock on Windows acts on SQLite side files another local user places beside its database (Oct 23, 2026).
On Windows, `ReadWriteLock` and `AsyncReadWriteLock` (the SQLite-backed reader/writer lock) connect SQLite to the lock database by its path, in every directory. SQLite derives three side files from that path: ` -journal`, the rollback journal (pages saved to undo an interrupted write); ` -wal`, the write-ahead log (changes kept outside the main file); and ` -shm`, the shared-memory index of the WAL. SQLite acts on whichever of these it finds beside the database before the lock runs any statement. Another local account that can create files in the database's directory, but not delete files of other accounts there, places such a side file beside the database and denies everyone `DELETE` on it, which a file's creator may do. `C:\Windows\Temp` (the temporary directory of services, granting `BUILTIN\Users` create but not delete) and `C:\Users\Public` are such directories.

With a `-wal` in place, every `read_lock()` and `write_lock()` of the user running the lock (below: the lock user) raises `sqlite3.OperationalError: disk I/O error` at once, whatever `timeout` says, until that account removes its file; the lock user cannot. With a `-journal` beside a lock database that holds a table, SQLite replays the journal and deletes the file the journal names, a file of the lock user, and the acquire reports success. Affected versions are filelock 3.20.4 through 4.2.0 on Windows. The maintainers found this while reviewing the fix for the POSIX form of the defect, GHSA-v4x8-3wr5-3wq8, whose text says "Windows does not take this path" (review round 4, finding F2 of set D). It is not among the findings of the report Anthropic's OSS Scanner sent on 15 October 2026.
CVSS 3.3 (version 3.1; evidence as of Oct 23, 2026; https://github.com/advisories/GHSA-9vhv-jxww-xfm5).
Sources:
GitHub-reviewed advisory GHSA-9vhv-jxww-xfm5: https://github.com/advisories/GHSA-9vhv-jxww-xfm5
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-112913.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 20:55 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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