What’s Vulnerable › Vulnerabilities

CVE-2026-15806: `HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching

• Severity: medium (CVSS 6.0 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-18 · updated 2026-10-22
• Weakness: CWE-319

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.

Affected products

• Python: before 3.10.22; from 3.11.0 before 3.11.17; from 3.12.0 before 3.12.15; from 3.13.0 before 3.13.16; from 3.14.0 before 3.14.8; from 3.15.0a1 before 3.15.0rc2 — fixed in 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8, 3.15.0rc2

How to fix

Upgrade to a fixed version: Python 3.10.22, 3.11.17, 3.12.15, 3.13.16. Check the vendor advisory for mitigations.

References

• https://github.com/python/cpython/commit/641be42bb07921ba0f8bffe228b1dc706b092ef6
• https://github.com/python/cpython/commit/851cf9a7142ecbdd39f831055533f58284ad2bcc
• https://github.com/python/cpython/commit/95355ee3a8e1d3c3d4858d1973aa42a9b91a2801
• https://github.com/python/cpython/commit/a0d023fbd23773e24b35d8368789470e22cda5d8
• https://github.com/python/cpython/commit/a2773a34183b7d94a243bb98fd658926cc5348ce
• https://github.com/python/cpython/commit/a7bb524fef61f77ede01f660ffbd591e1d5837ce
• https://github.com/python/cpython/commit/dac88d8615078c55f1304ea4c7a2d822700d4e5a
• https://github.com/python/cpython/issues/155694
• https://github.com/python/cpython/pull/155696
• https://mail.python.org/archives/list/security-announce@python.org/thread/3OKPE5S75KDNA7FY7AI3PL2MXM2X5RB3/
• http://www.openwall.com/lists/oss-security/2026/08/18/3
• https://github.com/python/cpython/issues/155694

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