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NVD / CVE Program· CNA GitHub_M

CVE-2025-68146: filelock has TOCTOU race condition that allows symlink attacks during lock file creation

Noroxi assessment

Priority: Monitor (action score 26/100)

  • 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: 0.19% (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 3.20.1; azl3 python-filelock 3.14.0-1 on Azure Linux 3.0 3.20.1-1; cbl2 python-filelock 3.0.12-13 3.0.12-14.

Low priority for now. Upgrade to tox-dev filelock 3.20.1; azl3 python-filelock 3.14.0-1 on Azure Linux 3.0 3.20.1-1; cbl2 python-filelock 3.0.12-13 3.0.12-14 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. In versions prior to 3.20.1, a Time-of-Check-Time-of-Use (TOCTOU) race condition allows local attackers to corrupt or truncate arbitrary user files through symlink attacks. The vulnerability exists in both Unix and Windows lock file creation where filelock checks if a file exists before opening it with O_TRUNC. An attacker can create a symlink pointing to a victim file in the time gap between the check and open, causing os.open() to follow the symlink and truncate the target file. All users of filelock on Unix, Linux, macOS, and Windows systems are impacted. The vulnerability cascades to dependent libraries. The attack requires local filesystem access and ability to create symlinks (standard user permissions on Unix; Developer Mode on Windows 10+). Exploitation succeeds within 1-3 attempts when lock file paths are predictable. The issue is fixed in version 3.20.1. If immediate upgrade is not possible, use SoftFileLock instead of UnixFileLock/WindowsFileLock (note: different locking semantics, may not be suitable for all use cases); ensure lock file directories have restrictive permissions (chmod 0700) to prevent untrusted users from creating symlinks; and/or monitor lock file directories for suspicious symlinks before running trusted applications. These workarounds provide only partial mitigation. The race condition remains exploitable. Upgrading to version 3.20.1 is strongly recommended.

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Dec 16, 2025
Updated
Jun 17, 2026
EPSS
0.1% · 9th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
6.5
CNA · GitHub_M
6.3
0.2 point gap

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

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

Get told when this record changes

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

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-68146

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

Affected versions

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

  • tox-dev filelockbefore 3.20.1

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

    • < 3.20.1affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12python-filelockbefore 3.9.0-1+deb12u13.9.0-1+deb12u1
Debian:13python-filelockbefore 3.18.0-1+deb13u13.18.0-1+deb13u1
Debian:14python-filelockbefore 3.20.2-13.20.2-1
openSUSE:Leap 15.6python-filelockbefore 3.12.2-150400.10.8.13.12.2-150400.10.8.1
openSUSE:Leap 16.0python-filelockbefore 3.18.0-160000.3.13.18.0-160000.3.1
openSUSE:Tumbleweedpython-filelockbefore 3.20.2-1.13.20.2-1.1
openSUSE:Tumbleweedpython-virtualenvbefore 20.36.1-1.120.36.1-1.1
PyPIfilelockbefore 3.20.13.20.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7python-filelockbefore 3.0.12-150100.3.6.13.0.12-150100.3.6.1
SUSE:Linux Enterprise Module for Python 3 15 SP7python-filelockbefore 3.12.2-150400.10.8.13.12.2-150400.10.8.1
SUSE:Linux Enterprise Server 16.0python-filelockbefore 3.18.0-160000.3.13.18.0-160000.3.1

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 own
    28Monitor
  • CVE-2026-112911filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user created first, losing mutual exclusion
    25Monitor
  • CVE-2026-112937filelock: ReadWriteLock on the hard-link route deletes any directory another user renames onto its .filelock-* link directory name
    24Monitor

Published before and after this one in the same product

  • Later →CVE-2026-22701Jan 10, 2026 · filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock
    21Monitor
  • Later →CVE-2026-112906Oct 20, 2026 · filelock: SoftFileLock evicts a fresh lock file whose watched age another local user's pre-dated file passed on through inode reuse
    18Monitor
  • Later →CVE-2026-112909Oct 20, 2026 · filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock path
    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 filelock3.20.1 · descriptionVendor (CNA)
azl3 python-filelock 3.14.0-1 on Azure Linux 3.03.20.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 python-filelock 3.0.12-133.0.12-14 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 python-filelock 3.0.12-13 on CBL Mariner 2.03.0.12-14 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 python-filelock 3.0.12-13 on CBL-Mariner 2.03.0.12-14 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:python-filelock3.9.0-1+deb12u1 · Debian:12Package registry (OSV)
opensuse:python-filelock3.12.2-150400.10.8.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:python-virtualenv20.36.1-1.1 · openSUSE:TumbleweedPackage registry (OSV)
PyPI:filelock3.20.1Package registry (OSV)
suse:python-filelock3.0.12-150100.3.6.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7Package registry (OSV)
suse:python-filelock3.12.2-150400.10.8.1 · SUSE:Linux Enterprise Module for Python 3 15 SP7Package 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.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

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

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

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

  • CVE-2026-112936308 days apartfilelock: ReadWriteLock follows a symlink at the lock path into SQLite
    24Monitor
  • CVE-2026-2270125 days apartfilelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock
    21Monitor
  • CVE-2026-112912308 days apartfilelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists and is writable by the lock taker
    10Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

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

Weakness class (CWE)

CWE-59 · Improper Link Resolution Before File Access ('Link Following')

CVSS vector

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

nvd-primary

Attack context

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

Change log

  1. Fix✗ → ✓

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References

Show all references (2 more)

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

All records