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CVE-2026-112909— filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock path

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 是一个跨平台的 Python 文件锁工具。在 4.2.1 版本之前，UnixFileLock 在以下情况下可能会截断被重命名到锁路径的普通文件：当另一个本地用户拥有实际的重命名权限，或在宽松的硬链接策略下存在硬链接时；此外，若请求了明确的文件模式，受影响的 3.10.2 及后续版本还可能更改该文件的权限模式。该问题已在 4.2.1 版本中修复。

CVSS 6.1 · Medium
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I. Basic Information for CVE-2026-112909

Vulnerability Information
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Vulnerability Title
filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-links onto the lock path
Source: CVE Program / CVE List V5
Vulnerability Description
filelock is a platform-independent file lock for Python. Prior to 4.2.1, UnixFileLock can truncate a regular file renamed onto the lock path when another local user has actual rename permission, or hard-linked there under a permissive hard-link policy; when an explicit mode is requested, affected versions from 3.10.2 can also change that file's mode. This issue is fixed in version 4.2.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
使用不正确的解析名称或索引
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
tox-dev filelock < 4.2.1 -

II. Public POCs for CVE-2026-112909

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III. Intelligence Information for CVE-2026-112909

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Other References for CVE-2026-112909 (4)

Same Patch Batch · tox-dev · 2026-10-20 · 13 CVEs total

CVE-2026-112940 7.1 HIGH filelock ReadWriteLock: SQLite reopens the lock database by name, so a planted symlink or
CVE-2026-112911 6.3 MEDIUM filelock: StrictSoftFileLock and SoftReadWriteLock adopt a protocol directory another user
CVE-2026-112934 6.1 MEDIUM filelock: SoftReadWriteLock holder refresh writes through a hard link and hangs on a named
CVE-2026-112936 6.1 MEDIUM filelock: ReadWriteLock follows a symlink at the lock path into SQLite
CVE-2026-112937 6.1 MEDIUM filelock: ReadWriteLock on the hard-link route deletes any directory another user renames
CVE-2026-112915 5.5 MEDIUM filelock ReadWriteLock: a crafted lock database makes every acquire stall or hang regardle
CVE-2026-112914 5.3 MEDIUM filelock: SoftFileLock stale-break restore follows a swapped-in symbolic link and hard-lin
CVE-2026-112906 4.7 MEDIUM filelock: SoftFileLock evicts a fresh lock file whose watched age another local user's pre
CVE-2026-112935 4.7 MEDIUM filelock: SoftFileLock stale-lock break removes a live lock file on a reused inode number
CVE-2026-112939 4.7 MEDIUM filelock: SoftFileLock removes a live holder's marker when another user forges the PID in
CVE-2026-112941 3.3 LOW filelock: SoftReadWriteLock follows a lock tree swapped in after its first acquire and wri
CVE-2026-112912 2.5 LOW filelock: Symlink swap during SoftFileLock's writability check leaks whether a path exists

IV. Related Vulnerabilities

Same product: filelock
Same vendor: tox-dev
Same weakness: CWE-706

V. Comments for CVE-2026-112909

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