---
id: CVE-2026-15806
title: >-
  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 reque…
summary: >-
  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 reque…
severity: medium
cvss: 6
cvssVector: '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'
cwe:
  - CWE-319
  - CWE-522
vendor: Python Software Foundation
product: CPython
affected:
  - CPython < 3.12.15
  - CPython >= 3.13.0 < 3.13.16
  - CPython >= 3.14.0 < 3.14.8
  - CPython >= 3.15.0a1 < 3.15.0rc2
published: '2026-08-18'
updated: '2026-10-01'
sourceUpdated: '2026-10-01T01:16:36.283'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-15806'
references:
  - url: >-
      https://github.com/python/cpython/commit/641be42bb07921ba0f8bffe228b1dc706b092ef6
    label: cna@python.org
  - url: >-
      https://github.com/python/cpython/commit/851cf9a7142ecbdd39f831055533f58284ad2bcc
    label: cna@python.org
  - url: >-
      https://github.com/python/cpython/commit/95355ee3a8e1d3c3d4858d1973aa42a9b91a2801
    label: cna@python.org
  - url: >-
      https://github.com/python/cpython/commit/a0d023fbd23773e24b35d8368789470e22cda5d8
    label: cna@python.org
  - url: >-
      https://github.com/python/cpython/commit/a2773a34183b7d94a243bb98fd658926cc5348ce
    label: cna@python.org
  - url: >-
      https://github.com/python/cpython/commit/a7bb524fef61f77ede01f660ffbd591e1d5837ce
    label: cna@python.org
  - url: >-
      https://github.com/python/cpython/commit/dac88d8615078c55f1304ea4c7a2d822700d4e5a
    label: cna@python.org
  - url: 'https://github.com/python/cpython/issues/155694'
    label: cna@python.org
  - url: 'https://github.com/python/cpython/pull/155696'
    label: cna@python.org
  - url: >-
      https://mail.python.org/archives/list/security-announce@python.org/thread/3OKPE5S75KDNA7FY7AI3PL2MXM2X5RB3/
    label: cna@python.org
  - url: 'http://www.openwall.com/lists/oss-security/2026/08/18/3'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://github.com/python/cpython/issues/155694'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-08-18T18:56:36.349726Z'
cvssSource: cna
epss: 0.00451
epssPercentile: 0.36753
ingestedAt: '2026-09-30T23:29:32.575Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.