CVE-2026-113726: pypa virtualenv · OS Command Injection
Affects pypa virtualenvSource CVE Database V5
Not known to be exploited · CVSS 7.8 High : upgrade to 21.14.4 soon.
Data as of 26 Oct 2026, 17:30 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 21.14.4
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 20 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade pypa virtualenv to 21.14.4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| pypavirtualenv | Affected
| Fixed in
|
PyPIvirtualenvpkg:pypi/virtualenvOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
This vulnerability is fixed in virtualenv version 21.14.4. Users should upgrade to version 21.14.4 or later to remediate this issue. No other mitigation is required if upgrading is possible. Users of zsh with PROMPT_SUBST disabled or bash are not affected by this vulnerability.
Description
### 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.