Vulnerability · Published Apr 1, 2026 · Assigned by GitHub_M
CVE-2026-34531Flask-HTTPAuth invokes token verification callback when missing or empty token was given by client
Medium 6.5
In plain English
A medium-severity improper authentication in Flask-HTTPAuth from miguelgrinberg. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | python-flask-httpauth | no fix listed | DEBIAN-CVE-2026-34531 |
| Debian:13 | python-flask-httpauth | no fix listed | DEBIAN-CVE-2026-34531 |
| Debian:14 | python-flask-httpauth | 4.8.1-1.1 | DEBIAN-CVE-2026-34531 |
| PyPI | flask-httpauth | 4.8.1 | GHSA-p44q-vqpr-4xmg |
| PyPI | flask-httpauth | 4.8.1 | PYSEC-2026-2152 |
| Ubuntu:22.04:LTS | python-flask-httpauth | no fix listed | UBUNTU-CVE-2026-34531 |
| Ubuntu:24.04:LTS | python-flask-httpauth | no fix listed | UBUNTU-CVE-2026-34531 |
| Ubuntu:25.10 | python-flask-httpauth | no fix listed | UBUNTU-CVE-2026-34531 |
| Ubuntu:26.04:LTS | python-flask-httpauth | no fix listed | UBUNTU-CVE-2026-34531 |
| Ubuntu:26.10 | python-flask-httpauth | no fix listed | UBUNTU-CVE-2026-34531 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| miguelgrinberg | Flask-HTTPAuth | < 4.8.1 |
Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N
References
- https://github.com/miguelgrinberg/Flask-HTTPAuth/security/advisories/GHSA-p44q-vqpr-4xmg x_refsource_CONFIRM
- https://github.com/miguelgrinberg/flask-httpauth/commit/b15ffe9e50e110d7174ccd944f642079e1dcf9ee x_refsource_MISC
- https://github.com/miguelgrinberg/Flask-HTTPAuth/releases/tag/v4.8.1 x_refsource_MISC
- https://lists.debian.org/debian-lts-announce/2026/05/msg00049.html