CVE-2026-15806
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure.
- Exploit odds
- 0.5% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.5% in the next 30 days (EPSS).
- Severity: 6.0 MEDIUM (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.5% · EPSS, next 30 days
- Weakness
- CWE-319 · Cleartext transmission
- Record status
- Awaiting Analysis
Attack profile CVSS 4.0 · 6.0
- Attack vector
- Network
- Complexity
- High
- Attack requirements
- Present
- Privileges needed
- None
- User interaction
- Passive
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Raw 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-15806.md and follow it. Check whether this project is affected by CVE-2026-15806. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- 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/pull/155696
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/[email protected]/thread/3OKPE5S75KDNA7FY7AI3PL2MXM2X5RB3/
- http://www.openwall.com/lists/oss-security/2026/08/18/3
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
- https://github.com/python/cpython/issues/155694