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Using default SSLContext for HTTPS requests in an HTTPS proxy doesn't verify certificate hostname for proxy connection

Moderate severity GitHub Reviewed Published Mar 15, 2021 in urllib3/urllib3 • Updated Jun 21, 2024

Package

pip urllib3 (pip)

Affected versions

>= 1.26.0, < 1.26.4

Patched versions

1.26.4

Description

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:

References

@sethmlarson sethmlarson published to urllib3/urllib3 Mar 15, 2021
Published by the National Vulnerability Database Mar 15, 2021
Reviewed Mar 19, 2021
Published to the GitHub Advisory Database Mar 19, 2021
Last updated Jun 21, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS score

0.137%
(50th percentile)

Weaknesses

CVE ID

CVE-2021-28363

GHSA ID

GHSA-5phf-pp7p-vc2r

Source code

Credits

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