Using default SSLContext for HTTPS requests in an HTTPS proxy doesn't verify certificate hostname for proxy connection
Impact
Users who are using an HTTPS proxy to issue HTTPS requests and haven't configured their own SSLContext via proxy_config.
Only the default SSLContext is impacted.
Patches
urllib3 >=1.26.4 has the issue resolved. urllib3<1.26 is not impacted due to not supporting HTTPS requests via HTTPS proxies.
Workarounds
Upgrading is recommended as this is a minor release and not likely to break current usage.
Configuring an SSLContext with check_hostname=True and passing via proxy_config instead of relying on the default SSLContext
For more information
If you have any questions or comments about this advisory:
- Email us at sethmichaellarson@gmail.com
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Python (PyPI) | urllib3 | >= 1.26.0, < 1.26.4 | 1.26.4 |
Referencias
- https://github.com/urllib3/urllib3/commits/main
- https://pypi.org/project/urllib3/1.26.4/
- https://github.com/urllib3/urllib3/commit/8d65ea1ecf6e2cdc27d42124e587c1b83a3118b0
- https://github.com/urllib3/urllib3/security/advisories/GHSA-5phf-pp7p-vc2r
- https://nvd.nist.gov/vuln/detail/CVE-2021-28363
- https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2021-59.yaml
- https://github.com/pypa/advisory-db/tree/main/vulns/urllib3/PYSEC-2021-59.yaml
- https://github.com/urllib3/urllib3
- https://github.com/urllib3/urllib3/blob/main/CHANGES.rst#1264-2021-03-15
- https://github.com/urllib3/urllib3/releases/tag/1.26.4
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4S65ZQVZ2ODGB52IC7VJDBUK4M5INCXL
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4S65ZQVZ2ODGB52IC7VJDBUK4M5INCXL
- https://pypi.org/project/urllib3/1.26.4
- https://security.gentoo.org/glsa/202107-36
- https://security.gentoo.org/glsa/202305-02
- https://security.netapp.com/advisory/ntap-20240621-0007
- https://www.oracle.com/security-alerts/cpuoct2021.html
- Vector CVSS
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N- Debilidad (CWE)
CWE-295- Plataforma
- Python (PyPI)
- Paquete
urllib3- Publicada
- 15.03.2021
- Actualizado
- 11.10.2026 13:19
Fuentes y licencias
OSV / GitHub Advisory Database - PYSEC-2021-59 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5phf-pp7p-vc2r - CC BY 4.0
Historial de vulnerabilidades: urllib3
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
- 22
- Primera → última
- 01.2017 09.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 1
- Alta 11
- Media 10
Divulgaciones por año
- 2017: 1
- 2018: 1
- 2019: 2
- 2020: 2
- 2021: 2
- 2022: 0
- 2023: 3
- 2024: 1
- 2025: 4
- 2026: 6
-
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