CVE-2026-112935: filelock is a platform-independent file lock for Python

Q: How do I fix CVE-2026-112935?

filelock: upgrade to 4.2.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-112935 being exploited?

CVE-2026-112935 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-112935 affect?

CVE-2026-112935 affects filelock. Severity is medium (CVSS 4.7). filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, SoftFileLock can break a stale marker after an attacker frees its own marker following the stale read, an honest contender creates a live successor on the reu

Q: How urgent is CVE-2026-112935?

Priority 22/100. Public exploit reference

Routine

MEDIUM 4.7UPGRADE

CVE-2026-112935 is a medium-severity flaw (CVSS 4.7) affecting filelock. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, SoftFileLock can break a stale marker after an attacker frees its own marker following the stale read, an honest contender creates a live successor on the reused inode, and the successor's modification time is not newer than the saved observation, causing the live marker to be removed and two holders to be admitted. This issue is fixed in version 4.2.1.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	4.7 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.1% (top 97%)
CISA exploited list	No
Weakness	CWE-367
Published	2026-10-20
Last modified	2026-10-21

Publisher (CNA): GitHub, Inc. · Vendor: tox-dev

Last updated 2026-10-21 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-20 15:17 UTCPublished CVE record published
2026-10-21 21:12 UTCUpdated Record last modified

tox-dev filelock UPGRADE

Affected: >= 3.22.0 and < 4.2.1

Fixed in: 4.2.1

Safe to downgrade to: a release before 3.22.0

1. Check installed version

pip show filelock

2. UPGRADE to 4.2.1

pip install --upgrade "filelock>=4.2.1"

3. If no update is available yet, DOWNGRADE to a release before 3.22.0

pip index versions filelock pip install "filelock<3.22.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-112935?

filelock: upgrade to 4.2.1. Exact commands for each OS are on this page.

Is CVE-2026-112935 being exploited?

CVE-2026-112935 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-112935 affect?

CVE-2026-112935 affects filelock. Severity is medium (CVSS 4.7). filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, SoftFileLock can break a stale marker after an attacker frees its own marker following the stale read, an honest contender creates a live successor on the reu

How urgent is CVE-2026-112935?

Priority 22/100. Public exploit reference

Software pages

Python vulnerabilities

Related CVEs

CVE-2026-112940 HIGH 7.1 UPGRADE filelock is a platform-independent file lock for Python
CVE-2026-112934 MEDIUM 6.1 UPGRADE filelock is a platform-independent file lock for Python
CVE-2026-112911 MEDIUM 6.3 UPGRADE filelock is a platform-independent file lock for Python
CVE-2026-112912 LOW 2.5 UPGRADE filelock is a platform-independent file lock for Python
CVE-2026-112914 MEDIUM 5.3 UPGRADE filelock is a platform-independent file lock for Python

References

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