Vulnerability · Published Aug 18, 2026 · Assigned by PSF
CVE-2026-15806`HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching
Medium 6.0
In plain English
A medium-severity security flaw in CPython from Python Software Foundation. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.21 | python3 | 3.12.15-r0 | ALPINE-CVE-2026-15806 |
| Alpine:v3.22 | python3 | 3.12.15-r0 | ALPINE-CVE-2026-15806 |
| Alpine:v3.23 | python3 | 3.12.15-r0 | ALPINE-CVE-2026-15806 |
| Alpine:v3.24 | python3 | 3.14.8-r0 | ALPINE-CVE-2026-15806 |
| Debian:12 | pypy3 | no fix listed | DEBIAN-CVE-2026-15806 |
| Debian:13 | pypy3 | no fix listed | DEBIAN-CVE-2026-15806 |
| Debian:14 | pypy3 | 8.0.1+dfsg-1 | DEBIAN-CVE-2026-15806 |
| Debian:12 | python3.11 | 3.11.2-6+deb12u9 | DEBIAN-CVE-2026-15806 |
| Debian:13 | python3.13 | no fix listed | DEBIAN-CVE-2026-15806 |
| Debian:14 | python3.14 | 3.14.7-3 | DEBIAN-CVE-2026-15806 |
| Debian:14 | python3.15 | 3.15.0~rc2-1 | DEBIAN-CVE-2026-15806 |
| Ubuntu:22.04:LTS | python3.10 | no fix listed | UBUNTU-CVE-2026-15806 |
| Ubuntu:24.04:LTS | python3.12 | no fix listed | UBUNTU-CVE-2026-15806 |
| Ubuntu:26.04:LTS | python3.14 | no fix listed | UBUNTU-CVE-2026-15806 |
| Ubuntu:26.10 | python3.14 | no fix listed | UBUNTU-CVE-2026-15806 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Python Software Foundation | CPython | 0 – before 3.10.223.11.0 – before 3.11.173.12.0 – before 3.12.153.13.0 – before 3.13.163.14.0 – before 3.14.83.15.0a1 – before 3.15.0rc2 |
Weakness: CWE-319, CWE-522 · 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
References
- https://github.com/python/cpython/issues/155694 issue-tracking
- https://github.com/python/cpython/pull/155696 patch
- https://mail.python.org/archives/list/security-announce@python.org/thread/3OKPE5S75KDNA7FY7AI3PL2MXM2X5RB3/ vendor-advisory
- https://github.com/python/cpython/commit/a0d023fbd23773e24b35d8368789470e22cda5d8 patch
- https://github.com/python/cpython/commit/a2773a34183b7d94a243bb98fd658926cc5348ce patch
- https://github.com/python/cpython/commit/a7bb524fef61f77ede01f660ffbd591e1d5837ce patch
- https://github.com/python/cpython/commit/641be42bb07921ba0f8bffe228b1dc706b092ef6 patch
- https://github.com/python/cpython/commit/851cf9a7142ecbdd39f831055533f58284ad2bcc patch
- https://github.com/python/cpython/commit/95355ee3a8e1d3c3d4858d1973aa42a9b91a2801 patch
- https://github.com/python/cpython/commit/dac88d8615078c55f1304ea4c7a2d822700d4e5a patch
- http://www.openwall.com/lists/oss-security/2026/08/18/3