filelock: StrictSoftFileLock creates its claim directories without the lock mode, so another local user with a write bit on them can end a…
- Exploited
- No known exploitation
- Fix
- Fixed in 4.2.1
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 4.2.1.
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 25/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
The filelock Python library's StrictSoftFileLock and AsyncStrictSoftFileLock on POSIX systems create their claim directories without the caller's restrictive lock mode, so a local user with low privileges can delete an active holder's claims or plant malformed ones. This lets another process acquire the lock while the original holder is still in its critical section, or blocks acquisition altogether.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
filelock is a platform-independent file lock for Python. From version 3.30.0 until version 4.2.1, StrictSoftFileLock and AsyncStrictSoftFileLock on POSIX systems create coordination and claim directories without applying the caller’s restrictive lock mode. A permissive umask or inherited default ACL can leave these directories writable by another local user, allowing that user to delete an active holder’s claims. Another authorized process can then acquire the lock while the original holder remains in its critical section. An attacker can also plant malformed claims to prevent acquisition. This issue is fixed in version 4.2.1.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure?/25Unknown. No advisory context yet
- Reach20/20filelock: 138.8M downloads a week
- Severity5.3/10CVSS 5.3
- No patch0/5No signal
What would change the score
- Would score about 80 if added to CISA KEV
- Would score about 75 if CISA's SSVC rates exploitation active
- Would score about 47 if advisories confirm default setups are exposed
Impact
- Widely used
filelock has 138.8m weekly downloads.Source: pypistats.org
47.2k packages depend on filelock.Source: deps.dev
What to do
Upgrade to a fixed version: 4.2.1.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- tox-dev filelock
From 3.30.0 · fixed in 4.2.1
- filelockPyPI
From 3.30.0 · fixed in 4.2.1
Evidence 5
- Advisory
- Repository
- Repository
- Repository
- Repository
Corrections
None so far.
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Questions about CVE-2026-112908
Is CVE-2026-112908 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-112908?
filelock: from 3.30.0 before 4.2.1. filelock (PyPI): from 3.30.0 before 4.2.1.Source: cve.now feed data
How do I fix CVE-2026-112908?
Upgrade to a fixed version: 4.2.1.Source: cve.now feed data