Medium 4.7Published Oct 20, 2026

CVE-2026-112939filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker

Updated under an hour ago (Oct 28, 2026, 10:40 AM ET)

Does this affect you?

It affects tox-dev filelock and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for tox-dev filelock

Exploited in the last 30 days

filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, SoftFileLock can trust a forged process identifier in a marker that an attacker can modify but cannot remove, allowing an authorized contender such as another process of the holder's account or root to act as a confused deputy, remove the live marker, and admit another holder. This issue is fixed in version 4.2.1.

CVSS: 4.7 MEDIUM (v3.1, CNA)CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE): CWE-345
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Oct 20, 2026
First seen by InfoSec Signals: Oct 20, 2026

Affected products

Affected products

tox-dev filelock tox_dev:filelock (from the name)	from 3.22.0, < 4.2.1	CNA record
tox-dev filelock tox-dev:filelock	from 3.22.0 before 4.2.1	NVD

References

References

https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4	x-refsource-confirm, exploit, mitigation, patch, vendor-advisory
https://github.com/tox-dev/filelock/pull/836	x-refsource-misc, patch
https://github.com/tox-dev/filelock/commit/eeceaa846cbe4df72718d94c8371ca1ab8f5b3cc	x-refsource-misc, patch
https://github.com/tox-dev/filelock/releases/tag/4.2.1	x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.