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.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-1411 advisory.

    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. (CVE-2025-68146)

    filelock is a platform-independent file lock for Python. Prior to version 3.20.3, a TOCTOU race condition     vulnerability exists in the SoftFileLock implementation of the filelock package. An attacker with local     filesystem access and permission to create symlinks can exploit a race condition between the permission     validation and file creation to cause lock operations to fail or behave unexpectedly. The vulnerability     occurs in the _acquire() method between raise_on_not_writable_file() (permission check) and os.open()     (file creation). During this race window, an attacker can create a symlink at the lock file path,     potentially causing the lock to operate on an unintended target file or leading to denial of service. This     issue has been patched in version 3.20.3. (CVE-2026-22701)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-1415 advisory.

    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. (CVE-2025-68146)

    filelock is a platform-independent file lock for Python. Prior to version 3.20.3, a TOCTOU race condition     vulnerability exists in the SoftFileLock implementation of the filelock package. An attacker with local     filesystem access and permission to create symlinks can exploit a race condition between the permission     validation and file creation to cause lock operations to fail or behave unexpectedly. The vulnerability     occurs in the _acquire() method between raise_on_not_writable_file() (permission check) and os.open()     (file creation). During this race window, an attacker can create a symlink at the lock file path,     potentially causing the lock to operate on an unintended target file or leading to denial of service. This     issue has been patched in version 3.20.3. (CVE-2026-22701)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Ubuntu 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-7999-1 advisory.

    It was discovered that Filelock incorrectly handled symlinks in temp files. A local attacker could     possibly use this issue to cause lock operations to fail or behave unexpectedly. (CVE-2026-22701)

    It was discovered that the file locking implementation in the Filelock package contained a race condition.
    A local attacker could possibly use this to cause a denial of service or corrupt arbitrary user files.
    (CVE-2025-68146)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote openSUSE 16 host has a package installed that is affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:20144-1 advisory.

    - CVE-2025-68146: TOCTOU race condition may allow local attackers to corrupt or truncate arbitrary user     files (bsc#1255244).
    - CVE-2026-22701: TOCTOU race condition in the SoftFileLock implementation (bsc#1256457).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 / openSUSE 15 host has a package installed that is affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:0220-1 advisory.

    - CVE-2025-68146: TOCTOU race condition may allow local attackers to corrupt or truncate arbitrary user     files (bsc#1255244).
    - CVE-2026-22701: TOCTOU race condition in the SoftFileLock implementation (bsc#1256457).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has a package installed that is affected by a vulnerability as referenced in the SUSE-SU-2026:0082-1 advisory.

    - CVE-2025-68146: TOCTOU race condition may allow local attackers to corrupt or truncate arbitrary user     files (bsc#1255244).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2025-68146)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
299516	Amazon Linux 2023 : python3.13-filelock (ALAS2023-2026-1411)	Nessus	Amazon Linux Local Security Checks	medium
298128	Amazon Linux 2023 : python3-filelock (ALAS2023-2026-1415)	Nessus	Amazon Linux Local Security Checks	medium
297797	Ubuntu 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS : Filelock vulnerabilities (USN-7999-1)	Nessus	Ubuntu Local Security Checks	medium
297782	openSUSE 16 Security Update : python-filelock (openSUSE-SU-2026:20144-1)	Nessus	SuSE Local Security Checks	medium
296442	SUSE SLED15 / SLES15 / openSUSE 15 Security Update : python-filelock (SUSE-SU-2026:0220-1)	Nessus	SuSE Local Security Checks	medium
282543	SUSE SLED15 / SLES15 Security Update : python-filelock (SUSE-SU-2026:0082-1)	Nessus	SuSE Local Security Checks	medium
278912	Linux Distros Unpatched Vulnerability : CVE-2025-68146	Nessus	Misc.	medium

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