TI-2026-76854 Aliases CVE-2026-112912 GHSA-9j6q-wvj5-jgjg

Symlink following in filelock SoftFileLock leaks path existence

MEDIUM 46CWE-59Published 2026-10-20 · Updated 2026-10-20

Key facts

Attack vector: Local
Privileges required: Low
User interaction: None
Attack complexity: High
Impact type: Information disclosure
Confidentiality · integrity · availability: Low · None · 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-59 and the CVSS impact.

Summary

The filelock Python package from 3.32.6 before 4.2.1 is affected. SoftFileLock follows a symbolic link that another process swaps in during its writability check, which is a link following flaw (CWE-59). A local user with low privileges can infer whether a chosen path exists and is writable from the result of a lock acquisition, on certain platform and directory configurations. 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 3.32.6 until 4.2.1, SoftFileLock can follow a swapped symbolic link during the conditional os.access writability check for a node without its owner-write bit, allowing another local user on a platform and directory configuration that follows the link to infer whether a chosen path exists and is writable from the observable acquisition result. This issue is fixed in version 4.2.1.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00213 11th 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	3.32.6 to before 4.2.1	4.2.1	Patch available	CNA
—	filelock (PyPI)	3.32.6 to before 4.2.1	4.2.1	Patch available	GHSA-9j6q-wvj5-jgjg

filelock Vendortox-dev Affected 3.32.6 to before 4.2.1 Fixed in 4.2.1 Patch available CNA
filelock (PyPI) Vendor— Affected 3.32.6 to before 4.2.1 Fixed in 4.2.1 Patch available GHSA-9j6q-wvj5-jgjg

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:tox-dev:filelock::::::python::*	3.32.6 to before 4.2.1	Vulnerable	tox-dev

cpe:2.3:a:tox-dev:filelock:*:*:*:*:*:python:*:* Versions 3.32.6 to before 4.2.1 Vulnerable ·tox-dev

Remediation

Upgrade the PyPI package filelock to version 4.2.1, which fixes the issue. The sources list no fixed version for Ansible Automation Orchestrator 2026, Lightspeed Core, Lightspeed Services for Advanced Cluster Management, OpenShift Lightspeed and Pen Drive Powered by Red Hat Lightspeed, and other products. Red Hat has no fix 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-9j6q-wvj5-jgjg filelock (PyPI) Fixed in 4.2.1 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Low. 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-2026-112912
2026-10-21 Affected versions changed · Red Hat
2026-10-21 CVSS score added · Red Hat
2026-10-28 Alias added: GHSA-9j6q-wvj5-jgjg
2026-10-28 Fix available: PyPI/[email protected] · GHSA-9j6q-wvj5-jgjg
2026-10-28 CVSS score added · GHSA-9j6q-wvj5-jgjg
2026-10-28 Weakness changed · GHSA-9j6q-wvj5-jgjg
2026-10-28 6 new references · GHSA-9j6q-wvj5-jgjg

References

Exploit 1

https://github.com/tox-dev/filelock/security/advisories/GHSA-9j6q-wvj5-jgjg

Patch 2

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-112912

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

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