TI-2026-76861 Aliases CVE-2026-112939 GHSA-rfpc-qcw5-3pc4

SoftFileLock in filelock trusts forged PIDs and removes live markers

MEDIUM 55CWE-345Published 2026-10-20 · Updated 2026-10-20

Key facts

Attack vector: Local
Privileges required: Low
User interaction: None
Attack complexity: High
Impact type: Security bypass
Confidentiality · integrity · availability: None · High · None
Fix status: Partial Red Hat: 15 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-345.

Summary

filelock from 3.22.0 before 4.2.1 is affected. SoftFileLock trusts a forged process identifier stored in a marker that an attacker can modify but not remove (CWE-345). A local contender with authorized access, such as another process under the holder's account or root, can remove the live marker and let another holder acquire the lock. A public exploit is linked in the references.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.0014 3rd percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Partial filelock (tox-dev): 4.2.1filelock (PyPI): 4.2.1Red Hat: 15 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
tox-dev	filelock	3.22.0 to before 4.2.1	4.2.1	Patch available	CNA
—	filelock (PyPI)	3.22.0 to before 4.2.1	4.2.1	Patch available	GHSA-rfpc-qcw5-3pc4

filelock Vendortox-dev Affected 3.22.0 to before 4.2.1 Fixed in 4.2.1 Patch available CNA
filelock (PyPI) Vendor— Affected 3.22.0 to before 4.2.1 Fixed in 4.2.1 Patch available GHSA-rfpc-qcw5-3pc4

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:tox-dev:filelock::::::python::*	3.22.0 to before 4.2.1	Vulnerable	tox-dev

cpe:2.3:a:tox-dev:filelock:*:*:*:*:*:python:*:* Versions 3.22.0 to before 4.2.1 Vulnerable ·tox-dev

Remediation

Upgrade the PyPI package filelock to version 4.2.1, which fixes this issue. Red Hat lists no available fix for Ansible Automation Orchestrator 2026, Lightspeed Core, OpenShift Lightspeed, Red Hat AI Inference Server and other products, and no fix is planned for Exploit Intelligence.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Fix · CNA filelock (tox-dev) Fixed in 4.2.1
Fix · GHSA-rfpc-qcw5-3pc4 filelock (PyPI) Fixed in 4.2.1 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Ansible Automation Orchestrator 2026	Affected	No fix yet: Fix deferred
Exploit Intelligence	Affected	No fix planned: Out of support scope
Lightspeed Core	Affected	No fix yet: Fix deferred
Lightspeed Services for Advanced Cluster Management	Affected	No fix yet: Fix deferred
OpenShift Lightspeed	Affected	No fix yet: Fix deferred
Pen Drive Powered by Red Hat Lightspeed	Affected	No fix yet: Fix deferred
Red Hat AI Inference Server	Affected	No fix yet: Fix deferred
Red Hat Ansible Automation Platform 2	Affected	No fix yet: Fix deferred
Red Hat Ansible Automation Platform Ansible Core 2	Affected	No fix yet: Fix deferred
Red Hat Enterprise Linux AI (RHEL AI) 3	Affected	No fix yet: Fix deferred
Red Hat Lightspeed Services for OCP	Affected	No fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)	Affected	No fix yet: Fix deferred
Red Hat OpenShift Container Platform 4	Affected	No fix yet: Fix deferred
Red Hat OpenShift Dev Spaces	Affected	No fix yet: Fix deferred
Red Hat Satellite 6	Affected	No fix yet: Fix deferred

Timeline

2026-10-20 Threatist record created from CVE-2026-112939
2026-10-21 Affected versions changed · Red Hat
2026-10-21 CVSS score added · Red Hat
2026-10-28 Alias added: GHSA-rfpc-qcw5-3pc4
2026-10-28 Fix available: PyPI/[email protected] · GHSA-rfpc-qcw5-3pc4
2026-10-28 CVSS score added · GHSA-rfpc-qcw5-3pc4
2026-10-28 Weakness changed · GHSA-rfpc-qcw5-3pc4
2026-10-28 6 new references · GHSA-rfpc-qcw5-3pc4

References

Exploit 1

https://github.com/tox-dev/filelock/security/advisories/GHSA-rfpc-qcw5-3pc4

Patch 2

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-112939

Other 2

TI-2026-76862 Symlink race in filelock ReadWriteLock lets attackers overwrite files CVSS 3.1HIGH 7.1
TI-2026-76853 filelock soft locks adopt directories created by other local users CVSS 3.1MEDIUM 6.3
TI-2026-76859 Symlink following in filelock ReadWriteLock redirects SQLite database CVSS 3.1MEDIUM 6.1
TI-2026-76857 Unsafe holder record refresh in filelock SoftReadWriteLock CVSS 3.1MEDIUM 6.1
TI-2026-76852 filelock UnixFileLock truncates files placed on the lock path CVSS 3.1MEDIUM 6.1
TI-2026-76856 Crafted lock database makes filelock ReadWriteLock acquisitions hang CVSS 3.1MEDIUM 5.5

See all 14 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences