The urllib3 library 1.26.x before 1.26.4 for Python omits SSL certificate validation in…
Priority LOW 33CWE-295Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Spoofing
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Partial Red Hat: 1 fixed, 1 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-295.
Summary
The urllib3 library 1.26.x before 1.26.4 for Python omits SSL certificate validation in some cases involving HTTPS to HTTPS proxies. The initial connection to the HTTPS proxy (if an SSLContext isn't given via proxy_config) doesn't verify the hostname of the certificate. This means certificates for different servers that still validate properly with the default urllib3 SSLContext will be silently accepted.
Why it matters now
EPSS 0.02166 82nd percentileScored 2026-11-08
Fix Partial urllib3 (PyPI): 1.26.4Red Hat: 1 fixed, 1 without a fix
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
| — | urllib3 (PyPI) | 1.26.0 to before 1.26.4 | 1.26.4 | Patch available | GHSA-5phf-pp7p-vc2r |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
- urllib3 (PyPI) Vendor— Affected 1.26.0 to before 1.26.4 Fixed in 1.26.4 Patch available GHSA-5phf-pp7p-vc2r
CPE configurations NVD · 3
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:* | 1.26.0 to before 1.26.4 | Vulnerable | python-pillow |
| cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* | 34 | Vulnerable | Fedoraproject |
| cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.59:*:*:*:*:*:*:* | 8.59 | Vulnerable | Oracle |
- cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:* Versions 1.26.0 to before 1.26.4 Vulnerable ·python-pillow
- cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* Versions 34 Vulnerable ·Fedoraproject
- cpe:2.3:a:oracle:peoplesoft_enterprise_peopletools:8.59:*:*:*:*:*:*:* Versions 8.59 Vulnerable ·Oracle
Remediation
- Fix · GHSA-5phf-pp7p-vc2r urllib3 (PyPI) Fixed in 1.26.4 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenShift Container Platform 4 | Affected | No fix planned: Out of support scope |
| Red Hat OpenShift Container Platform 3.11 | Fixed | — |
Not affected: 10 products
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 3.11
- Red Hat OpenStack Platform 10 (Newton)
- Red Hat OpenStack Platform 13 (Queens)
- Red Hat Quay 3
- Red Hat Software Collections
- Red Hat Storage 3
Timeline
- 2026-10-02 Threatist record created from CVE-2021-28363
- 2026-10-03 Alias added: GHSA-5phf-pp7p-vc2r
References
Patch 3
Advisory 6
Other 10
- https://security.netapp.com/advisory/ntap-20240621-0007/
- 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/[email protected]/message/4S65ZQVZ2ODGB52IC7VJDBUK4M5INCXL
- https://pypi.org/project/urllib3/1.26.4
- https://security.netapp.com/advisory/ntap-20240621-0007
Sources
- CVE-2021-28363 · CVE Program
- CVE-2021-28363 · NVD
- FIRST EPSS
- GHSA-5phf-pp7p-vc2r · GitHub Advisory Database · CC BY 4.0
- CVE-2021-28363 · Red Hat security data · CC BY 4.0
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