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CVE.org (no NVD analysis yet)· CNA GitHub_M

CVE-2026-112935: filelock: SoftFileLock stale-lock break removes a live lock file on a reused inode number and admits two holders

MediumCVSS 4.7 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 18/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.13% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: tox-dev filelock 4.2.1.

Low priority for now. Upgrade to tox-dev filelock 4.2.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Oct 20, 2026
Updated
Oct 28, 2026
EPSS
0.1% · 2th percentile

Report tools

JSON

Action score

18

Monitor

Low priority for now.

CVSS
18 / 40 · 4.7 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
4.7
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
tox-devfilelock

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • tox-dev filelock

    • >= 3.22.0, < 4.2.1affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • tox-dev filelock3.22.0 and later · before 4.2.1

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12python-filelockfrom 0—
Debian:14python-filelockbefore 4.2.8-14.2.8-1
openSUSE:Tumbleweedpython-filelockbefore 4.2.4-1.14.2.4-1.1
PyPIfilelockfrom 3.22.0 · before 4.2.14.2.1

Same product

tox-dev: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-112940filelock ReadWriteLock: SQLite reopens the lock database by name, so a planted symlink or journal file makes the lock user's process overwrite or unlink its…
    28Monitor
  • CVE-2025-68146filelock has TOCTOU race condition that allows symlink attacks during lock file creation
    26Monitor
  • CVE-2026-112911filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion
    25Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-112915Oct 20, 2026 · filelock ReadWriteLock: a crafted lock database makes every acquire stall or hang regardless of timeout
    22Monitor
  • ← EarlierCVE-2026-112934Oct 20, 2026 · filelock: SoftReadWriteLock holder refresh writes through a hard link and hangs on a named pipe that another local user renames over its record
    24Monitor
  • Later →CVE-2026-112936Oct 20, 2026 · filelock: ReadWriteLock follows a symlink at the lock path into SQLite
    24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
tox-dev filelock4.2.1 · descriptionVendor (CNA)
debian:python-filelock4.2.8-1 · Debian:14Package registry (OSV)
opensuse:python-filelock4.2.4-1.1 · openSUSE:TumbleweedPackage registry (OSV)
PyPI:filelock4.2.1Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 12, 2026+23 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-1129370 days apartfilelock: ReadWriteLock on the hard-link route deletes any directory another user renames onto its .filelock-* link directory name
    24Monitor
  • CVE-2026-1129410 days apartfilelock: SoftReadWriteLock follows a lock tree swapped in after its first acquire and writes lock records into directories of the user running the lock
    13Monitor
  • CVE-2026-11291316 days apartfilelock: ReadWriteLock on Windows acts on SQLite side files another local user places beside its database
    13Monitor

Not on record for this CVE: researcher credit · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-367 · Time-of-check Time-of-use (TOCTOU) Race Condition

CVSS vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. SSVC exploitation— → poc
  2. Exploit maturity— → none
  3. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records