Description
The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also used for requests to the same host over http://, so an attacker able to redirect or downgrade a client to plain HTTP (for example, via an HTTPS-to-HTTP redirect or an on-path position) could capture credentials in cleartext. Credentials added for http:// URLs could likewise be sent over https://.

Credential matching is now scoped by URL scheme. Credentials registered with a URL that includes a scheme are only used for requests with the same scheme. Credentials registered with a bare authority (such as example.com or example.com:8080) continue to match any scheme, preserving compatibility with existing code, including proxy authentication.

Users who cannot upgrade immediately can mitigate by ensuring that applications never make plain http:// requests to hosts for which credentials are registered, for example by not following redirects to http:// URLs.
Published: 2026-08-18
Score: 6 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Tue, 18 Aug 2026 19:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 18 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
References

Tue, 18 Aug 2026 18:15:00 +0000


Tue, 18 Aug 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Python
Python cpython
Vendors & Products Python
Python cpython

Tue, 18 Aug 2026 16:00:00 +0000

Type Values Removed Values Added
Description The HTTPPasswordMgr class in the urllib.request module, along with its subclasses HTTPPasswordMgrWithDefaultRealm and HTTPPasswordMgrWithPriorAuth, did not take the URL scheme into account when matching stored credentials against a requested URL. Credentials added for an https:// URL were also used for requests to the same host over http://, so an attacker able to redirect or downgrade a client to plain HTTP (for example, via an HTTPS-to-HTTP redirect or an on-path position) could capture credentials in cleartext. Credentials added for http:// URLs could likewise be sent over https://. Credential matching is now scoped by URL scheme. Credentials registered with a URL that includes a scheme are only used for requests with the same scheme. Credentials registered with a bare authority (such as example.com or example.com:8080) continue to match any scheme, preserving compatibility with existing code, including proxy authentication. Users who cannot upgrade immediately can mitigate by ensuring that applications never make plain http:// requests to hosts for which credentials are registered, for example by not following redirects to http:// URLs.
Title `HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching
Weaknesses CWE-319
CWE-522
References
Metrics cvssV4_0

{'score': 6, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: PSF

Published:

Updated: 2026-08-18T18:56:57.585Z

Reserved: 2026-07-15T08:49:13.390Z

Link: CVE-2026-15806

cve-icon Vulnrichment

Updated: 2026-08-18T18:07:31.778Z

cve-icon NVD

Status : Received

Published: 2026-08-18T16:17:02.220

Modified: 2026-08-18T19:16:44.547

Link: CVE-2026-15806

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-18T17:30:15Z

Weaknesses
  • CWE-319

    Cleartext Transmission of Sensitive Information

  • CWE-522

    Insufficiently Protected Credentials