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CVE-2026-22701— filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock

Quick assessment

Affected
tox-dev filelock
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

filelock是tox development team开源的一个Python文件锁。 filelock 3.20.3之前版本存在安全漏洞，该漏洞源于SoftFileLock实现中存在TOCTOU竞争条件，可能导致锁定操作失败或行为异常。

CVSS 5.3 · Medium EPSS 0.13% · P2

Possible ATT&CK Techniques 1 AI

T1052.006
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I. Basic Information for CVE-2026-22701

Vulnerability Information
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Vulnerability Title
filelock Time-of-Check-Time-of-Use (TOCTOU) Symlink Vulnerability in SoftFileLock
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
在文件访问前对链接解析不恰当(链接跟随)
Source: CVE Program / CVE List V5
Vulnerability Title
filelock 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
filelock是tox development team开源的一个Python文件锁。 filelock 3.20.3之前版本存在安全漏洞，该漏洞源于SoftFileLock实现中存在TOCTOU竞争条件，可能导致锁定操作失败或行为异常。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
tox-dev filelock < 3.20.3 -

II. Public POCs for CVE-2026-22701

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III. Intelligence Information for CVE-2026-22701

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Vendor Advisories for CVE-2026-22701 (1)

IV. Related Vulnerabilities

Same product: filelock
Same vendor: tox-dev
Same weakness: CWE-59

V. Comments for CVE-2026-22701

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