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BIT-virtualenv-2026-113723 — virtualenv: Bash prompt values can change meaning under older compatibility modes

2026-10-31T15:22:10.273934+00:00

Affected: Bitnami: virtualenv

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.14.9, caller-supplied prompt text can become executable syntax in the bash activation prompt. An attacker must influence the value passed to virtualenv, and a user must subsequently activate the environment and draw the prompt. This vulnerability is fixed in 21.14.9.

CVE-2026-113723 — virtualenv: Bash prompt values can change meaning under older compatibility modes

2026-10-31T15:22:10.273994+00:00

Affected: pypa virtualenv

GHSA-6w3r-xr62-4xcp — virtualenv: Bash prompt values can change meaning under older compatibility modes

2026-10-31T15:22:10.274027+00:00

Affected: PyPI: virtualenv

## Summary

Caller-supplied prompt text can become executable syntax in the bash activation prompt. An attacker must influence the value passed to virtualenv, and a user must subsequently activate the environment and draw the prompt.

## Affected area

Bash runs with compatibility level 4.2 and draws the environment prompt. Its replacement-string behavior differs from newer compatibility modes, leaving prompt text subject to a second interpretation. The report concerns POSIX activation. It does not establish exposure through unrelated activators.

## Attacker-controlled input

The attacker controls prompt or destination data passed as a virtualenv argument. The user later sources the generated activation script.

## Affected code

The relevant 21.14.8 source is in [bash prompt assembly](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/activation/bash/activate.sh).

## Mechanism

`bin/activate` copies the prompt into `PS1`. A shell expands `PS1` again when it draws a prompt, so the value must survive both the assignment and that later expansion. The bash and zsh branches escape for their usual prompt rules. Three other paths still interpret prompt data as commands: dash sourcing `activate` directly, a child dash inheriting an exported `PS1` from bash, and bash running at compatibility level 4.2 or lower. A value such as `x$(touch MARKER)y` then runs `touch` on prompt display. Creating the environment does not run the payload.

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