Auth bypass in Miguelgrinberg Flask-Httpauth
CVE-2026-34531
Flask-HTTPAuth provides Basic, Digest and Token HTTP authentication for Flask routes. Prior to version 4.8.1, in a situation where the client makes a request to a token protected resource without passing a token, or passing an empty token, Flask-HTTPAuth would invoke the application's token verification callback function with the token argument set to an empty string. If the application had any users in its database with an empty string set as their token, then it could potentially authenticate the client request against any of those users. This issue has been patched in version 4.8.1.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N.
EPSS exploit prediction
EPSS: 0.005 (39.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Miguelgrinberg Flask-Httpauth — versions < 4.8.1
Weakness classification (CWE)
References
- github.com/miguelgrinberg/Flask-HTTPAuth/security/advisories/GHSA-p44q-vqpr-4xmg (Mitigation, Vendor Advisory)
- github.com/miguelgrinberg/flask-httpauth/commit/b15ffe9e50e110d7174ccd944f64207… (Patch)
- github.com/miguelgrinberg/Flask-HTTPAuth/releases/tag/v4.8.1 (Product, Release Notes)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2026-34531?
- CVE-2026-34531 is a medium-severity vulnerability in Miguelgrinberg Flask-Httpauth, classified under Improper Authentication. CVSS score: 6.5/10. Published 2026-04-01.
- How severe is CVE-2026-34531?
- Medium severity. CVSS v3 base score is 6.5 out of 10.