virtualenv: Venv configuration readback can reinterpret path boundaries

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.

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.14.9, the stdlib venv creator reads generated pyvenv.cfg with str.splitlines() and merges parsed keys over virtualenv's selected configuration. An untrusted caller who influences the destination pathname can include a line-boundary character such as U+2028 to inject keys including home and include-system-site-packages, causing path data to change configuration structure before final output. Setting include-system-site-packages to true weakens environment isolation, while an altered home can change which standard-library files the interpreter loads if the attacker also controls that location. The builtin creator does not use this readback path. This issue is fixed in version 21.14.9.

Source published

20 Oct 2026 19:42:55 UTC

Source modified

23 Oct 2026 02:01:48 UTC

Observed here

23 Oct 2026 16:01:20 UTC

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CVSS 4.0 · 2.0 CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N