CVE-2026-102937: virtualenv Command Injection Vulnerability

HIGH
Advisory Identifier: GHSA-x78j-v8h9-3j2q
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CWE-78
Published
Advisory Summary

CVE-2026-102937 is a HIGH command injection vulnerability (CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')) affecting virtualenv libraries in the PyPI ecosystem. The issue involves command injection via --prompt in activate.bat (batch activator). Remediation is available by upgrading affected packages to version 21.7.12.

CVE-2026-102937 at a Glance

CVE Identifier CVE-2026-102937
GHSA Identifier GHSA-x78j-v8h9-3j2q
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Affected Product virtualenv
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix CVE-2026-102937

To remediate this vulnerability, upgrade all affected virtualenv dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

virtualenv fixed: 21.7.12 
pip install virtualenv>=21.7.12
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show virtualenv

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-102937, inspect your installed packages using pip:

pip show virtualenv

Analyze the terminal output to locate any version of virtualenv in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 21.7.12), your application is affected.

Note: The pip show virtualenv command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'), where the product constructs all or part of an os command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended os command when it is sent to a downstream component. In virtualenv, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

`BatchActivator.quote()` returned its input unchanged, the only activator with no escaping at all. `--prompt`, the `VIRTUALENV_PROMPT` environment variable, and the config file all set the prompt, and `activate.bat` writes it straight into `@set "VAR=value"`. A prompt containing a double quote closes that string early, and whatever follows runs as live cmd.exe syntax: ```console $ virtualenv --prompt 'x" & calc & "' venv $ venv\Scripts\activate.bat ``` runs `calc` the moment someone activates the environment. Confirmed on a real Windows runner. Anyone who templates a prompt from untrusted input (a CI job using a branch name, a wrapper script deriving an environment name from user input) hands an attacker code execution in the shell of anyone who activates the resulting venv on Windows. Fixed in 21.7.12 by escaping the characters cmd.exe treats as live syntax inside this construct. Fix: https://github.com/pypa/virtualenv/pull/3250

CVE-2026-102937 Affected virtualenv Versions

1 component(s)
Fixed Versions:
21.7.12
Product / Package Ecosystem Affected Versions Fixed Version
virtualenv
pypi/virtualenv
PyPI
< 21.7.12
21.7.12

References

GitHub Advisory / Wiki ADVISORY
https://github.com/pypa/virtualenv/security/advisories/GHSA-x78j-v8h9-3j2q
NVD — CVE-2026-102937 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-102937
virtualenv Source Repository REPOSITORY
https://github.com/pypa/virtualenv/pull/3250
Security Fix Commit FIX COMMIT
https://github.com/pypa/virtualenv/commit/d721ff140ce4afdc2a9b76751e4584e25d9fbea6
virtualenv Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/virtualenv/PYSEC-2026-4014.yaml
virtualenv Source Repository REPOSITORY
https://github.com/pypa/virtualenv
virtualenv Release RELEASE
https://github.com/pypa/virtualenv/releases/tag/21.7.12
pypi.org/project/virtualenv WEB
https://pypi.org/project/virtualenv

Frequently Asked Questions

What is CVE-2026-102937?
CVE-2026-102937 is a security vulnerability in virtualenv involving Command injection via --prompt in activate.bat (batch activator) under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection').
Which virtualenv versions are affected?
Affected versions include releases prior to 21.7.12 across affected packages: virtualenv.
What version fixes CVE-2026-102937?
Upgrading to 21.7.12 (or the latest patched release for your respective branch) resolves the vulnerability.
Is virtualenv affected?
Yes, virtualenv is affected in releases prior to 21.7.12. Upgrade your dependency to 21.7.12 or later.
What CWE is associated with CVE-2026-102937?
CVE-2026-102937 is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') (The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.).
How can I check PyPI dependencies for CVE-2026-102937?
Run the dependency tree command: 'pip show virtualenv'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x78j-v8h9-3j2q",
  "modified" : "2026-10-01T15:08:30Z",
  "published" : "2026-10-01T15:08:29Z",
  "aliases" : [ "CVE-2026-102937" ],
  "summary" : "virtualenv: Command injection via --prompt in activate.bat (batch activator)",
  "details" : "`BatchActivator.quote()` returned its input unchanged, the only activator with no escaping at all. `--prompt`, the `VIRTUALENV_PROMPT` environment variable, and the config file all set the prompt, and `activate.bat` writes it straight into `@set \"VAR=value\"`. A prompt containing a double quote closes that string early, and whatever follows runs as live cmd.exe syntax:\n\n```console\n$ virtualenv --prompt 'x\" & calc & \"' venv\n$ venv\\Scripts\\activate.bat\n```\n\nruns `calc` the moment someone activates the environment. Confirmed on a real Windows runner. Anyone who templates a prompt from untrusted input (a CI job using a branch name, a wrapper script deriving an environment name from user input) hands an attacker code execution in the shell of anyone who activates the resulting venv on Windows.\n\nFixed in 21.7.12 by escaping the characters cmd.exe treats as live syntax inside this construct. Fix: https://github.com/pypa/virtualenv/pull/3250",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "virtualenv"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "21.7.12"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 21.7.11"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pypa/virtualenv/security/advisories/GHSA-x78j-v8h9-3j2q"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-102937"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/virtualenv/pull/3250"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/virtualenv/commit/d721ff140ce4afdc2a9b76751e4584e25d9fbea6"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/virtualenv/PYSEC-2026-4014.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pypa/virtualenv"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/virtualenv/releases/tag/21.7.12"
  }, {
    "type" : "WEB",
    "url" : "https://pypi.org/project/virtualenv"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-78" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-01T15:08:29Z",
    "nvd_published_at" : "2026-09-29T21:17:18Z"
  }
}