filelock: SoftFileLock removes a live holder's marker when another user forges the PID in a writable marker

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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 published

20 Oct 2026 14:38:52 UTC

Source modified

20 Oct 2026 15:14:56 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 3.1 · 4.7 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N