virtualenv writes prompt values into pyvenv.cfg without sanitizing line boundaries, allowing configuration injection
pyvenv.cfg is a line-based format with no escape syntax. PyEnvCfg.write()
wrote values verbatim, while PyEnvCfg._read_values() parses the file with
str.splitlines(). A value containing a line boundary therefore became
additional configuration lines, and because reading is last-wins, the injected
keys replaced any key written earlier in the file.
The prompt value is the reachable input: it is set by --prompt, by the
VIRTUALENV_PROMPT environment variable, or from the config file, and
write() emits prompt before home. A crafted prompt can therefore set
home in the generated pyvenv.cfg. home is what tooling reads to locate
the base interpreter, so a consumer that trusts it can be pointed elsewhere.
implementation, version_info, version, executable, command and
virtualenv are also written before prompt and can be replaced the same
way.
This requires the prompt to come from somewhere other than the person running
the command, for example a CI job templating a branch name into it, tooling
deriving an environment name from user-supplied data, or an inherited
VIRTUALENV_PROMPT.
The boundary set is the one str.splitlines() recognizes, which is wider than
\n: \r, \v, \f, the file, group and record separators, U+0085,
U+2028 and U+2029 were all written through unchanged and all split the
line when read back.
Fixed in 21.7.11: PyEnvCfg.write() now collapses those boundaries to spaces
as it serializes each line, so it cannot emit a structurally invalid file
regardless of what a caller places in content.
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Python (PyPI) | virtualenv | < 21.7.11 | 21.7.11 |
Referencias
- https://github.com/pypa/virtualenv/security/advisories/GHSA-9h9j-4vrj-gf7g
- https://nvd.nist.gov/vuln/detail/CVE-2026-102938
- https://github.com/pypa/virtualenv/pull/3247
- https://github.com/pypa/virtualenv/commit/a30f995461043acb6cacbf3a890951563ccf7140
- https://github.com/pypa/advisory-database/tree/main/vulns/virtualenv/PYSEC-2026-4012.yaml
- https://github.com/pypa/virtualenv
- https://github.com/pypa/virtualenv/releases/tag/21.7.11
- https://pypi.org/project/virtualenv
- Vector CVSS
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N- Debilidad (CWE)
CWE-93- Plataforma
- Python (PyPI)
- Paquete
virtualenv- Publicada
- 17.09.2026
- Actualizado
- 11.10.2026 15:18
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-9h9j-4vrj-gf7g - CC BY 4.0
OSV / GitHub Advisory Database - PYSEC-2026-4012 - PyPA Advisory Database; CC BY 4.0
Historial de vulnerabilidades: virtualenv
Todas las vulnerabilidades publicadas de este paquete (Python (PyPI)), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 9
- Primera → última
- 12.2011 10.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Alta 6
- Media 3
Divulgaciones por año
- 2017: 0
- 2018: 0
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 1
- 2025: 0
- 2026: 7
antes: 1
-
virtualenv writes prompt values into pyvenv.cfg without sanitizing line boundaries, allowing configuration injection esta entrada
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