Upstream information
Description
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.SUSE information
Overall state of this security issue: Pending
This issue is currently rated as having moderate severity.
| CVSS detail | CNA (GitHub) | SUSE |
|---|---|---|
| Base Score | 6.3 | 4.7 |
| Vector | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N |
| Attack Vector | Local | Local |
| Attack Complexity | High | High |
| Privileges Required | Low | Low |
| User Interaction | None | None |
| Scope | Unchanged | Unchanged |
| Confidentiality Impact | None | None |
| Integrity Impact | High | High |
| Availability Impact | High | None |
| CVSSv3 Version | 3.1 | 3.1 |
| CVSS detail | SUSE |
|---|---|
| Base Score | 5.7 |
| Vector | CVSS:4.0/AV:L/AC:H/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N |
| Attack Vector | Local |
| Attack Complexity | High |
| Attack Requirements | None |
| Privileges Required | Low |
| User Interaction | None |
| Vulnerable System Confidentiality Impact | None |
| Vulnerable System Integrity Impact | High |
| Vulnerable System Availability Impact | None |
| Subsequent System Confidentiality Impact | None |
| Subsequent System Integrity Impact | None |
| Subsequent System Availability Impact | None |
| CVSSv4 Version | 4.0 |
Status of this issue by product and package
Please note that this evaluation state might be work in progress, incomplete or outdated. Also information for service packs in the LTSS phase is only included for issues meeting the LTSS criteria. If in doubt, feel free to contact us for clarification. The updates are grouped by state of their lifecycle. SUSE product lifecycles are documented on the lifecycle page.
| Product(s) | Source package | State |
|---|---|---|
| Products under general support and receiving all security fixes. | ||
| SUSE Linux Enterprise Desktop 15 SP6 | python-filelock | Affected |
| SUSE Linux Enterprise Desktop 15 SP7 | python-filelock | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP6 | python-filelock | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP7 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP6 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Development Tools 15 SP7 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP5 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP6 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP7 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Python 3 15 SP6 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Python 3 15 SP7 | python-filelock | Affected |
| SUSE Linux Enterprise Server 15 SP6 | python-filelock | Affected |
| SUSE Linux Enterprise Server 15 SP6-LTSS | python-filelock | Affected |
| SUSE Linux Enterprise Server 15 SP7 | python-filelock | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | python-filelock | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP7 | python-filelock | Affected |
| openSUSE Leap 15.6 | python-filelock | Affected |
| Products under Long Term Service Pack support and receiving important and critical security fixes. | ||
| SUSE Linux Enterprise High Performance Computing 15 SP4 | python-filelock | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | python-filelock | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5 | python-filelock | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | python-filelock | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | python-filelock | Affected |
| SUSE Linux Enterprise Module for Python 3 15 SP4 | python-filelock | Affected |
| SUSE Linux Enterprise Module for Python 3 15 SP5 | python-filelock | Affected |
| SUSE Linux Enterprise Server 15 SP4 | python-filelock | Affected |
| SUSE Linux Enterprise Server 15 SP4-LTSS | python-filelock | Affected |
| SUSE Linux Enterprise Server 15 SP5 | python-filelock | Affected |
| SUSE Linux Enterprise Server 15 SP5-LTSS | python-filelock | Affected |
| SUSE Manager Proxy 4.3 | python-filelock | Affected |
| SUSE Manager Retail Branch Server 4.3 | python-filelock | Affected |
| SUSE Manager Server 4.3 | python-filelock | Affected |
| Products past their end of life and not receiving proactive updates anymore. | ||
| SUSE Linux Enterprise Desktop 15 SP4 | python-filelock | Affected |
| SUSE Linux Enterprise Desktop 15 SP5 | python-filelock | Affected |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | python-filelock | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP4 | python-filelock | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | python-filelock | Affected |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | python-filelock | Affected |
| openSUSE Leap 15.3 | python-filelock | Affected |
| openSUSE Leap 15.4 | python-filelock | Affected |
| openSUSE Leap 15.5 | python-filelock | Affected |
SUSE Timeline for this CVE
CVE page created: Tue Dec 16 22:07:19 2025CVE page last modified: Thu Dec 18 16:01:15 2025