CVE-2026-15806 `HTTPPasswordMgr` can send saved HTTPS credentials via HTTP because of incorrect scheme matching
An attacker can capture HTTPS credentials in cleartext by downgrading connections to HTTP due to incorrect scheme matching in Python's urllib.request module.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-15806?
CVE-2026-15806 is a medium-severity vulnerability in CPython, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
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.
Which versions are affected by CVE-2026-15806?
3 open source packages ship an affected version, including libpython, python and python-min.
| Package | Affected | Fixed in |
|---|---|---|
libpython Bitnami | All versions | 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8 |
python Bitnami | All versions | 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8 |
python-min Bitnami | All versions | 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8 |
How do I fix CVE-2026-15806?
Upgrade libpython to a fixed version for your release line: 3.10.22, 3.11.17, 3.12.15 or 3.13.16.
Is CVE-2026-15806 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-15806 exists.
Sources
Also known as ALPINE-CVE-2026-15806, AZL-96867, BELL-CVE-2026-15806, BIT-libpython-2026-15806, BIT-python-2026-15806, BIT-python-min-2026-15806 and 10 more.