CVE-2026-102925: virtualenv bash and fish activation scripts execute commands embedded in paths

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-29 · updated 2026-09-30
Weakness: CWE-78

Description

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.7.13, the generated activate (bash and zsh) and activate.fish scripts place values already escaped by shlex.quote inside an additional quoted context. In the bash and zsh script, a crafted virtual environment path reaches __VIRTUAL_ENV__ when a relocated environment's recorded directory is absent; in the fish script, crafted Tcl or Tk library paths reach __TCL_LIBRARY__ or __TK_LIBRARY__. The surplus quotes can terminate the data-only quoted run and leave shell metacharacters parsed as commands when a user sources the activation script, allowing code execution with that user's privileges. This issue is fixed in version 21.7.13.

Affected products

Pypi Virtualenv: before 21.7.13; 0.8, 0.8.1, 0.8.2, 0.8.3, 0.8.4, 0.9 (+276) — fixed in 21.7.13
pypa virtualenv: before 21.7.13

How to fix

Upgrade to a fixed version: Pypi Virtualenv 21.7.13. Check the vendor advisory for mitigations.

References

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