HighCVE-2026-112940

Tox-dev Filelock: Race Condition Enabling Link Following (CVE-2026-112940)

Published 20.10.2026Last modified 22.10.2026Sources: Red Hat, Hersteller, OSV, CVE.org

Public exploit

What is affected, what to do

A flaw was found in filelock. When utilizing the ReadWriteLock mechanism, the component reopens SQLite database and auxiliary files by file path rather than retaining secure file descriptors.

An exploit is publicly available. Update filelock to version 4.2.1.

Affected: Tox-dev Filelock gte 3.20.4, < 4.2.1..*

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

7.1

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

7.1

CVSS v3

Severity High on the scale from 0 to 10.

Source: Red Hat, Hersteller, OSV, CVE.org

0.2 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 8.7

Show all metrics

Severity: High
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 66.10 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: PoC (publicly reported)
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 7.1 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 7.1
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.2 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 8.7; Low — this CVE sits in the lower 10% of all CVEs scored today.
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 20.10.2026
CISA assessment (SSVC): Exploitation: proof of concept · not automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 22 October 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-363, CWE-59

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

A flaw was found in filelock. When utilizing the ReadWriteLock mechanism, the component reopens SQLite database and auxiliary files by file path rather than retaining secure file descriptors. A local attacker with file renaming permissions in a shared directory can swap these filenames during operation, causing the application to delete or overwrite unintended files. This issue can result in unauthorized data modification, data loss, or a Denial of Service (DoS).

Source: redhat_csaf, GitHub Security Advisories, OSV (Open Source Vulnerabilities), NVD (NIST), cvelistv5

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
tox-dev	filelock	`≥ 3.20.4, < 4.2.1` `3.20.4 – < 4.2.1`	— `4.2.1`
pip	filelock	`>= 3.20.4, <= 4.2.0`	`4.2.1`
pypi	filelock	`4.0.0` `4.2.0` `3.30.1` `4.0.9` `4.0.10` `3.30.3` `4.0.7` `3.31.0` `3.25.2` `3.29.2` `4.0.6` `3.32.6` `3.23.0` `3.22.0` `3.32.7` `4.0.2` `3.28.0` `4.0.8` `3.31.1` `4.0.1` `3.31.2` `3.29.1` `3.20.4` `3.29.6` `3.32.4` `3.25.1` `4.0.5` `3.32.5` `4.1.1` `3.32.2` `4.0.4` `3.24.2` `4.0.3` `3.29.4` `3.29.0` `3.25.0` `4.1.2` `3.29.7` `4.0.12` `3.29.5` `3.30.0` `4.1.0` `3.32.3` `3.32.0` `3.24.1`	— — — — — — — — — — — — — — — — — — — — — — `4.2.1` — — — — — — — — — — — — — — — — — — — — — —

Vendors and products

Tox-dev Filelock

Weakness classes (CWE)

CWE-363Race Condition Enabling Link Following
Base
The product checks the status of a file or directory before accessing it, which produces a race condition in which the file can be replaced with a link before the access is performed, causing the product to access the wrong file.
Entry at MITRE CWE-363
CWE-59Improper Link Resolution Before File Access ('Link Following')
Base
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
Entry at MITRE CWE-59

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

Reference tagged as exploit	github.com (opens in a new tab)	PoC (publicly reported)reported, not verified	—

References & sources

github.comtox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2dx_refsource_MISC, Patch, web
github.comtox-dev/filelock/pull/834x_refsource_MISC, Patch, web
github.comtox-dev/filelock/releases/tag/4.2.1x_refsource_MISC, Release notes, web
github.comtox-dev/filelock/security/advisories/GHSA-v4x8-3wr5-3wq8x_refsource_CONFIRM, Exploit, Mitigation, Patch, Vendor advisory, web
NVD (NIST)vuln/detail/CVE-2026-112940advisory
github.comtox-dev/filelockpackage

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

22.10.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: proof of concept, automatable: no

New references:

https://github.com/tox-dev/filelock/security/advisories/GHSA-v4x8-3wr5-3wq8

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://github.com/tox-dev/filelock/security/advisories/GHSA-v4x8-3wr5-3wq8
SSVC assessment	added	—	{"id":"CVE-2026-112940","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-22T21:29:06.989000Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

21.10.2026Initial analysis by NVDNVD

Newly listed as affected:

Tox-dev Filelock (3.20.4 – before 4.2.1)

Weakness type: CWE-59

New references:

Show 6 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Weakness type (CWE)	added	—	CWE-59
Product configuration	added	—	OR cpe:2.3:a:tox-dev:filelock::::::python:: versions from (including) 3.20.4 up to (excluding) 4.2.1
Reference type	added	—	GitHub, Inc.: https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d Types: Patch
Reference type	added	—	GitHub, Inc.: https://github.com/tox-dev/filelock/pull/834 Types: Patch
Reference type	added	—	GitHub, Inc.: https://github.com/tox-dev/filelock/releases/tag/4.2.1 Types: Release Notes
Reference type	added	—	GitHub, Inc.: https://github.com/tox-dev/filelock/security/advisories/GHSA-v4x8-3wr5-3wq8 Types: Exploit, Mitigation, Patch, Vendor Advisory

Source identifier: nvd@nist.gov

20.10.2026ReceivedGitHub

CVSS V3.1: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Weakness type: CWE-363

Description added or changed

New references:

Show 8 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	filelock is a platform-independent file lock for Python. From 3.20.4 until 4.2.1, ReadWriteLock let SQLite reopen the database and side files by name; on POSIX systems an attacker with rename access in a non-sticky parent can swap those names to cause overwrite or unlink operations, while a writable adjacent hot journal is additionally required for attacker-chosen content overwrites. This issue is fixed in version 4.2.1.
CVSS	added	—	AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Weakness type (CWE)	added	—	CWE-363
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/112xxx/CVE-2026-112940.json">CVE-2026-112940</a>
Reference	added	—	https://github.com/tox-dev/filelock/commit/5e3f2ec0c5fb17cb2635b60b2b68bc63ab81ca2d
Reference	added	—	https://github.com/tox-dev/filelock/pull/834
Reference	added	—	https://github.com/tox-dev/filelock/releases/tag/4.2.1
Reference	added	—	https://github.com/tox-dev/filelock/security/advisories/GHSA-v4x8-3wr5-3wq8

Source identifier: security-advisories@github.com

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