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CVE-2026-112939— filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker

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 3.22.0 至 4.2.1 版本中，SoftFileLock 会信任标记文件中由攻击者伪造的进程标识符；攻击者虽无法删除该标记，但可对其进行篡改。这使得具备授权资格的竞争者（例如持有者账户下的其他进程或 root 用户）能够充当“混淆代理”（confused deputy），删除当前有效的标记，从而允许其他持有者获得锁。该问题已在 4.2.1 版本中修复。

CVSS 4.7 · Medium
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I. Basic Information for CVE-2026-112939

Vulnerability Information
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Vulnerability Title
filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker
Source: CVE Program / CVE List V5
Vulnerability Description
filelock is a platform-independent file lock for Python. From 3.22.0 until 4.2.1, SoftFileLock can trust a forged process identifier in a marker that an attacker can modify but cannot remove, allowing an authorized contender such as another process of the holder's account or root to act as a confused deputy, remove the live marker, and admit another holder. This issue is fixed in version 4.2.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对数据真实性的验证不充分
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
tox-dev filelock >= 3.22.0, < 4.2.1 -

II. Public POCs for CVE-2026-112939

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III. Intelligence Information for CVE-2026-112939

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Other References for CVE-2026-112939 (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-2026-112909 6.1 MEDIUM filelock: UnixFileLock truncates and chmods any regular file another user renames or hard-
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-2026-112941 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-345

V. Comments for CVE-2026-112939

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