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

Exp

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.

Published: 2025-12-16 Last update: 2026-03-05 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-68146 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.18%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2025-68146

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2025-68146

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.01% 0.18% +0.17%
2 2025-12-17 — 0.01% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-68146

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.0 5.2 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.0 5.5 [email protected]

Weakness enumeration for CVE-2025-68146

GitHub Security Advisory for CVE-2025-68146

GHSA-w853-jp5j-5j7f · Severity: medium · Ecosystem: pip — filelock has a TOCTOU race condition which allows symlink attacks during lock file creation

OS Trackers for CVE-2025-68146

vendor priority summary link
alpine — CVE-2025-68146: 1 source package rows (py3-filelock); 6 state rows across 3 repos (3.23-main, edge-community, edge-main); fixed 0, open 6. https://security.alpinelinux.org/vuln/CVE-2025-68146
debian not yet assigned CVE-2025-68146 not yet assigned priority: Debian including 1 source packages (python-filelock), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 3, open 2. https://security-tracker.debian.org/tracker/CVE-2025-68146
redhat medium — https://access.redhat.com/security/cve/CVE-2025-68146
suse medium CVE-2025-68146 severity moderate: SUSE including 24 source package names (2.1.3-5.8:e2fsprogs-1.47.0-3.1, 2.1.3-5.8:libcom_err2-1.47.0-3.1, …), 75 product×package rows across 43 product lines (Container suse/multi-linux-manager/5.1/x86_64/server, Container suse/sl-micro/6.0/baremetal-os-container, … (43 product lines)): Fixed 74, First Fixed 1. https://www.suse.com/security/cve/CVE-2025-68146/
ubuntu medium CVE-2025-68146 medium priority: Ubuntu including 1 source packages (python-filelock), 7 status rows across 7 suites (bionic, focal, jammy, noble, plucky, questing, upstream): released 4, ignored 1, needed 1, needs-triage 1. https://ubuntu.com/security/CVE-2025-68146

Affected software / configurations for CVE-2025-68146

Vendor Product Version Raw CPE
tox-dev filelock < 3.20.1 cpe:2.3:a:tox-dev:filelock:*:*:*:*:*:python:*:*

References for CVE-2025-68146

cvelogic Threat Intelligence