CVE-2026-113716: virtualenv: Builtin creation follows linked environment directories

Severity: medium (CVSS 4.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-20 · updated 2026-10-22
Weakness: CWE-59

Description

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.14.9, the builtin creator calls ensure_dir() for executable, library, and package directories, and ensure_dir() accepts an existing symlink to a directory because exists() follows it. Interpreter creation, seed installation, and activation generation then write through the linked parent outside the requested destination when another local account prepared the tree and the invoking user can access the target. The --clear option removes the planted tree first, while ordinary creation reaches it; arbitrary attacker-selected output bytes are not established. This issue is fixed in version 21.14.9.

Affected products

Pypi Virtualenv: before 21.14.9; 0.8, 0.8.1, 0.8.2, 0.8.3, 0.8.4, 0.9 (+298) — fixed in 21.14.9
pypa virtualenv: before 21.14.9

How to fix

Upgrade to a fixed version: Pypi Virtualenv 21.14.9. Check the vendor advisory for mitigations.

References

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