What’s Vulnerable › Vulnerabilities

CVE-2026-34531: Flask-HTTPAuth invokes token verification callback when missing or empty token was given by client

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-01 · updated 2026-10-26
• Weakness: CWE-287

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 products

• miguelgrinberg Flask-HTTPAuth: before 4.8.1 — fixed in 4.8.1

How to fix

Upgrade to a fixed version: miguelgrinberg Flask-HTTPAuth 4.8.1. Check the vendor advisory for mitigations.

References

• https://github.com/miguelgrinberg/Flask-HTTPAuth/releases/tag/v4.8.1
• https://github.com/miguelgrinberg/Flask-HTTPAuth/security/advisories/GHSA-p44q-vqpr-4xmg
• https://github.com/miguelgrinberg/flask-httpauth/commit/b15ffe9e50e110d7174ccd944f642079e1dcf9ee
• https://lists.debian.org/debian-lts-announce/2026/05/msg00049.html

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