filelock: WindowsFileLock ignores mode: a 0o600 lock file and the ReadWriteLock database inherit the directory ACL
- 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
Filelock, a platform-independent Python file-locking library, ignores the mode argument on Windows for WindowsFileLock lock files and the ReadWriteLock SQLite database, so they inherit the parent directory's access permissions. A local attacker with a low-privilege account that already has inherited access can read lock holder metadata or the lock database, modify those files where permissions allow writes, or take the lock after release to delay other processes.
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 3.10.0 until 4.2.1, filelock on Windows ignores the mode argument for WindowsFileLock files and the ReadWriteLock SQLite database. A lock created with mode=0o600 receives the parent directory's inheritable ACL because _open_non_reparse_fd and _nt_open do not create an owner-only security descriptor. Another local account with inherited access can read holder metadata or the lock database, modify those files where the ACL permits writes, or take the byte-range lock after release and delay later acquisitions. UnixFileLock is not affected, and mutual exclusion between cooperating processes continues to hold. 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 3.10.0 · fixed in 4.2.1
- filelockPyPI
From 3.10.0 · fixed in 4.2.1
Evidence 5
- Advisory
- Repository
- Repository
- Repository
- Repository
Corrections
None so far.
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Questions about CVE-2026-112910
Is CVE-2026-112910 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-2026-112910?
filelock: from 3.10.0 before 4.2.1. filelock (PyPI): from 3.10.0 before 4.2.1.Source: cve.now feed data
How do I fix CVE-2026-112910?
Upgrade to a fixed version: 4.2.1.Source: cve.now feed data