---
id: "CVE-2026-113726"
kind: "vulnerability"
aliases: ["CVE-2026-113726", "GHSA-5vjq-rrrf-7h2q"]
title: "virtualenv activate runs commands from the environment name in zsh with PROMPT_SUBST"
severity: "high"
cvss: 7.800000190734863
epss: 0.0023399998899549246
exploited: false
status: "open"
category: "package"
products: [{"name": "virtualenv", "fixed": ["21.14.4"], "affected": "<= 21.14.3", "ecosystem": "pypi"}]
ecosystems: ["pypi"]
tags: ["ci", "cwe-116", "cwe-78", "oh-my-zsh", "package", "python", "virtualenv", "zsh"]
not_affected_if: ["bash-only", "prompt-subst-off", "venv-not-activated-in-zsh"]
published_at: "2026-10-20T22:19:29+00:00"
first_seen_at: "2026-10-23T19:11:32+00:00"
updated_at: "2026-10-23T21:57:25+00:00"
sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-5vjq-rrrf-7h2q", "first_seen_at": "2026-10-23T19:11:32+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113726", "first_seen_at": "2026-10-23T21:57:25+00:00"}]
---

# virtualenv activate runs commands from the environment name in zsh with PROMPT_SUBST

virtualenv's bash activate script does not escape the environment name for zsh, so a name containing $(...), backticks or ${...} runs as shell commands each time the prompt is drawn when zsh PROMPT_SUBST is on. An attacker who can influence the environment path, --prompt or VIRTUALENV_PROMPT gets code execution in the victim's zsh session.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- pypi:virtualenv affected <= 21.14.3 fixed 21.14.4

## How to check

Run `echo $options[prompt_subst]` or `setopt | grep prompt_subst` in zsh to see if PROMPT_SUBST is on (oh-my-zsh enables it by default).
Run `pip show virtualenv` and check whether the version is 21.14.3 or lower.
List environment directory names and check for $, backtick or % characters, e.g. `ls -d */ | grep -E '[$`%]'`.

## Fix

Upgrade virtualenv to 21.14.4 or later.
Until then, set VIRTUAL_ENV_DISABLE_PROMPT=1 before sourcing activate, or run `unsetopt prompt_subst` in zsh.

## Timeline

- 2026-10-23T19:11:32+00:00 ghsa https://github.com/advisories/GHSA-5vjq-rrrf-7h2q
- 2026-10-23T21:57:25+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-113726

## From the sources

### Impact

zsh users activate an environment with the bash `activate` script, which puts the environment name into `PS1`. Since
21.13.0 the script escapes backslashes, dollar signs and backticks in that name, but only when `BASH_VERSION` is set, so
zsh gets the raw value. With the `PROMPT_SUBST` option set, zsh runs parameter expansion, command substitution and
arithmetic expansion on `PS1` each time it draws the prompt. A name that contains `$(...)`, backticks or `${...}` then
runs as commands in the user's shell, once per prompt.

The name comes from the environment directory, or from `--prompt` or `VIRTUALENV_PROMPT`. After you create an
environment with:

```console
$ virtualenv 'x$(touch PWNED)y'
```

`source 'x$(touch PWNED)y/bin/activate'` in a zsh session with `PROMPT_SUBST` set creates `PWNED`, and the prompt shows
`(xy)`. Passing that value as `--prompt` to an environment with a plain name has the same effect. Without
`PROMPT_SUBST`, zsh shows the name as text and runs nothing. bash runs nothing either.

A plain zsh starts with `PROMPT_SUBST` off. oh-my-zsh users have it on: oh-my-zsh loads
[`lib/theme-and-appearance.zsh`](https://github.com/ohmyzsh/ohmyzsh/blob/4d4cfc287e9d887b81242c0e431b5f49f9cec5c1/lib/theme-and-appearance.zsh#L5)
at startup, and that file sets it. An attacker needs to influence the environment path or prompt: a CI job or wrapper
tool that passes a branch, project or job name through, or a directory in a cloned repository or unpacked archive.
`--prompt .` takes the current directory's name.

zsh also reads `%` in `PS1` as a prompt escape, so a name with `%n` showed the user name in place of those characters,
though without running commands.

The bug is in releases up to and including 21.14.3. The payload runs on 20.26.6 and 21.14.3, and the reporter confirmed
21.9.1.

### Patches

Fixed in 21.14.4. Under zsh, `activate` now escapes the name the way it does under bash and doubles
`%`, so the example above runs nothing and the prompt shows the name as given. zsh gets the escaping even when
`PROMPT_SUBST` is off, because a user can set the option after activation; a name with a backslash, dollar sign or
backtick then shows the added backslashes.
Fix: https://github.com/pypa/virtualenv/commit/5b915367da82bd024b2a0d28d2f98007034b4aa2

### Workarounds

Set `VIRTUAL_ENV_DISABLE_PROMPT=1` before you source `activate`, which leaves `PS1` alone, or run
`unsetopt prompt_subst` if your prompt does not need it. Check the name of an environment you did not create before you
source its `activate`.

### Credits

Kaya Emre Arikan (@kemrec) reported this issue.

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