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VulnerabilityPublished Updated

CVE-2026-113776: Nox · virtualenv activation scripts run code from a path that contains a placeholder name

Affects noxSource GCVE Database

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Authoritative record:CVE-2026-113776· High 7.8

Not known to be exploited · CVSS 7.8 High : upgrade to 2026.8.17_1 soon.

Data as of 30 Oct 2026, 05:15 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.17.8
Patch
Available – fixed in 2026.8.17_1
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 29 Oct 2026.

What to do

Upgrade nox to 2026.8.17_1.

Affected software

ProductAffectedFixed in
Homebrewnoxpkg:brew/noxOther threatsAffected
  • >=2024.04.15 <2026.8.17_1
Fixed in
  • 2026.8.17_1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### 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.

References

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