PYSEC-2026-4014

Vulnerability from pysec - Published: 2026-09-18 01:41 - Updated: 2026-09-30 16:13
VLAI
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. For example, a venv created with --prompt 'x" & calc & "' runs calc the moment someone runs activate.bat.

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.

Impacted products
Name purl
virtualenv pkg:pypi/virtualenv
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "virtualenv",
        "purl": "pkg:pypi/virtualenv"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "21.7.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.8",
        "0.8.1",
        "0.8.2",
        "0.8.3",
        "0.8.4",
        "0.9",
        "0.9.1",
        "0.9.2",
        "1.0",
        "1.1",
        "1.10",
        "1.10.1",
        "1.11",
        "1.11.1",
        "1.11.2",
        "1.11.3",
        "1.11.4",
        "1.11.5",
        "1.11.6",
        "1.2",
        "1.3",
        "1.3.1",
        "1.3.2",
        "1.3.3",
        "1.3.4",
        "1.4",
        "1.4.1",
        "1.4.2",
        "1.4.3",
        "1.4.4",
        "1.4.5",
        "1.4.6",
        "1.4.7",
        "1.4.8",
        "1.4.9",
        "1.4rc1",
        "1.5",
        "1.5.1",
        "1.5.2",
        "1.6",
        "1.6.1",
        "1.6.2",
        "1.6.3",
        "1.6.4",
        "1.7",
        "1.7.1",
        "1.7.1.1",
        "1.7.1.2",
        "1.7.2",
        "1.8",
        "1.8.1",
        "1.8.2",
        "1.8.3",
        "1.8.4",
        "1.9",
        "1.9.1",
        "12.0",
        "12.0.1",
        "12.0.2",
        "12.0.4",
        "12.0.5",
        "12.0.6",
        "12.0.7",
        "12.1.0",
        "12.1.1",
        "13.0.0",
        "13.0.1",
        "13.0.2",
        "13.0.3",
        "13.1.0",
        "13.1.1",
        "13.1.2",
        "14.0.0",
        "14.0.1",
        "14.0.2",
        "14.0.3",
        "14.0.4",
        "14.0.5",
        "14.0.6",
        "15.0.0",
        "15.0.1",
        "15.0.2",
        "15.0.3",
        "15.1.0",
        "15.2.0",
        "16.0.0",
        "16.1.0",
        "16.2.0",
        "16.3.0",
        "16.3.1.dev0",
        "16.4.0",
        "16.4.1",
        "16.4.3",
        "16.4.4.dev0",
        "16.5.0",
        "16.6.0",
        "16.6.1",
        "16.6.2",
        "16.7.0",
        "16.7.1",
        "16.7.10",
        "16.7.11",
        "16.7.12",
        "16.7.2",
        "16.7.3",
        "16.7.4",
        "16.7.5",
        "16.7.6",
        "16.7.7",
        "16.7.8",
        "16.7.9",
        "20.0.0",
        "20.0.0b1",
        "20.0.0b2",
        "20.0.1",
        "20.0.10",
        "20.0.11",
        "20.0.12",
        "20.0.13",
        "20.0.14",
        "20.0.15",
        "20.0.16",
        "20.0.17",
        "20.0.18",
        "20.0.19",
        "20.0.2",
        "20.0.20",
        "20.0.21",
        "20.0.22",
        "20.0.23",
        "20.0.24",
        "20.0.25",
        "20.0.26",
        "20.0.27",
        "20.0.28",
        "20.0.29",
        "20.0.3",
        "20.0.30",
        "20.0.31",
        "20.0.32",
        "20.0.33",
        "20.0.34",
        "20.0.35",
        "20.0.4",
        "20.0.5",
        "20.0.6",
        "20.0.7",
        "20.0.8",
        "20.0.9",
        "20.1.0",
        "20.10.0",
        "20.11.0",
        "20.11.1",
        "20.11.2",
        "20.12.0",
        "20.12.1",
        "20.13.0",
        "20.13.1",
        "20.13.2",
        "20.13.3",
        "20.13.4",
        "20.14.0",
        "20.14.1",
        "20.15.0",
        "20.15.1",
        "20.16.0",
        "20.16.1",
        "20.16.2",
        "20.16.3",
        "20.16.4",
        "20.16.5",
        "20.16.6",
        "20.16.7",
        "20.17.0",
        "20.17.1",
        "20.18.0",
        "20.19.0",
        "20.2.0",
        "20.2.1",
        "20.2.2",
        "20.20.0",
        "20.21.0",
        "20.21.1",
        "20.22.0",
        "20.23.0",
        "20.23.1",
        "20.24.0",
        "20.24.1",
        "20.24.2",
        "20.24.3",
        "20.24.4",
        "20.24.5",
        "20.24.6",
        "20.24.7",
        "20.25.0",
        "20.25.1",
        "20.25.2",
        "20.25.3",
        "20.26.0",
        "20.26.1",
        "20.26.2",
        "20.26.3",
        "20.26.4",
        "20.26.5",
        "20.26.6",
        "20.27.0",
        "20.27.1",
        "20.28.0",
        "20.28.1",
        "20.29.0",
        "20.29.1",
        "20.29.2",
        "20.29.3",
        "20.3.0",
        "20.3.1",
        "20.30.0",
        "20.31.0",
        "20.31.1",
        "20.31.2",
        "20.32.0",
        "20.33.0",
        "20.33.1",
        "20.34.0",
        "20.35.0",
        "20.35.1",
        "20.35.2",
        "20.35.3",
        "20.35.4",
        "20.36.0",
        "20.36.1",
        "20.38.0",
        "20.39.0",
        "20.39.1",
        "20.4.0",
        "20.4.1",
        "20.4.2",
        "20.4.3",
        "20.4.4",
        "20.4.5",
        "20.4.6",
        "20.4.7",
        "20.5.0",
        "20.6.0",
        "20.7.0",
        "20.7.1",
        "20.7.2",
        "20.8.0",
        "20.8.1",
        "20.9.0",
        "21.0.0",
        "21.1.0",
        "21.2.0",
        "21.2.1",
        "21.2.2",
        "21.2.3",
        "21.2.4",
        "21.3.0",
        "21.3.1",
        "21.3.2",
        "21.3.3",
        "21.4.0",
        "21.4.1",
        "21.4.2",
        "21.4.3",
        "21.5.0",
        "21.5.1",
        "21.5.2",
        "21.6.0",
        "21.6.1",
        "21.7.0",
        "21.7.1",
        "21.7.10",
        "21.7.11",
        "21.7.2",
        "21.7.3",
        "21.7.4",
        "21.7.5",
        "21.7.6",
        "21.7.7",
        "21.7.8",
        "21.7.9"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-102937",
    "GHSA-x78j-v8h9-3j2q"
  ],
  "credits": [
    {
      "name": "Bern\u00e1t G\u00e1bor",
      "type": "FINDER"
    }
  ],
  "details": "`BatchActivator.quote()` returned its input unchanged, the only activator with\nno escaping at all. `--prompt`, the `VIRTUALENV_PROMPT` environment variable,\nand the config file all set the prompt, and `activate.bat` writes it straight\ninto `@set \"VAR=value\"`. A prompt containing a double quote closes that string\nearly, and whatever follows runs as live cmd.exe syntax. For example, a venv\ncreated with `--prompt \u0027x\" \u0026 calc \u0026 \"\u0027` runs `calc` the moment someone runs\n`activate.bat`.\n\nAnyone who templates a prompt from untrusted input (a CI job using a branch\nname, a wrapper script deriving an environment name from user input) hands an\nattacker code execution in the shell of anyone who activates the resulting venv\non Windows.\n\nFixed in 21.7.12 by escaping the characters cmd.exe treats as live syntax\ninside this construct.\n",
  "id": "PYSEC-2026-4014",
  "modified": "2026-09-30T16:13:20.593341Z",
  "published": "2026-09-18T01:41:45Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/pypa/virtualenv/security/advisories/GHSA-x78j-v8h9-3j2q"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/virtualenv/pull/3250"
    },
    {
      "type": "FIX",
      "url": "https://github.com/pypa/virtualenv/commit/d721ff140ce4afdc2a9b76751e4584e25d9fbea6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/virtualenv/releases/tag/21.7.12"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pypa/virtualenv"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/virtualenv"
    }
  ],
  "summary": "Command injection via --prompt in activate.bat (batch activator)"
}



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