CVE-2026-113776
highpriority · track · 0EPSS 0.003 · 19 %ileUSEPSS · scored 2026-10-27
virtualenv is a tool for creating isolated virtual python environments. From 20.26.6 until 21.14.2, ViaTemplateActivator.instantiate_template() replaces placeholders one key at a time across the complete activation template, so trigger names such as __VIRTUAL_NAME__, __VIRTUAL_ENV__, or __VIRTUAL_PROMPT__ inside an already substituted and quoted environment path or prompt can be replaced during a later pass. The later value's quoting can close the earlier literal and execute the remaining path when a user activates the environment through bash, fish, xonsh, or activate_this.py. The distinct csh prompt-display token __VIRTUAL_PROMPT_DISPLAY_TCSH__ can instead break the generated script without establishing command execution. The attacker must influence the destination path or --prompt, and a value without a relevant placeholder name does not trigger this mechanism. This issue is fixed in version 21.14.2.
cvss
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base score 0–10 · higher = more severe · hover a vector to decode
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affected products (1)
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advisories (1)
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- GHSA-8rjx-v5ww-45ppvirtualenv activation scripts run code from a path that contains a placeholder name2026-10-21ghsa · osvUS
### Impact `ViaTemplateActivator.instantiate_template` replaces the placeholders in an activation template one key at a time, each across the whole text. When a value that it already substituted and quoted contains the name of a later placeholder, the later pass rewrites that name inside the quoted literal. The inserted value brings its own quotes, which close the outer literal, and the rest of the path runs as code when a user activates the environment. `__VIRTUAL_NAME__` holds the environment's directory name, so a destination such as `A__VIRTUAL_NAME__B/x'$(touch PWNED)'y` is enough. In the default `activate` for bash, the `VIRTUAL_ENV` line renders as: ```sh VIRTUAL_ENV='/tmp/t/A'x'"'"'$(touch PWNED)'"'"'y'B/x'"'"'$(touch PWNED)'"'"'y' ``` Sourcing that script runs `touch PWNED`. The same payload in a path without the placeholder name runs nothing. `activate.fish` runs the command the same way, and the reporter also showed Python code execution through `activate.xsh` and `bin/activate_this.py`. In `activate.csh`, a directory named after a prompt display placeholder, such as `__VIRTUAL_PROMPT_DISPLAY_TCSH__`, breaks the script with `Unmatched '''`. No change to `quote()` can stop this, because the rewrite happens after `quote()` ran; it defeats `shlex.quote` and `repr()` alike. An attacker needs to influence the destination path or `--prompt`: a CI job or wrapper tool that builds the path from a branch or project name, or a directory in a cloned repository or unpacked archive. The bug affects versions 20.26.6 through 21.14.1. Version 20.26.6 first quoted template values (#2768) and introduced the per-key loop. ### Patches Fixed in 21.14.2. Activation scripts now keep a placeholder name in the environment's path or prompt as plain text, and activating the example above runs nothing. Fix: https://github.com/pypa/virtualenv/commit/602b26623a724827ff171bf11fef4ad186d01f74 ### Workarounds Do not create an environment whose path or `--prompt` contains a placeholder name such as `__VIRTUAL_NAME__`, `__VIRTUAL_ENV__` or `__VIRTUAL_PROMPT__`, and inspect the generated activation script before you source one you did not create. ### Credits Kevin Stubbings (@Kwstubbs) of GitHub Security Lab reported this issue.
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references (3) nvd
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