CVE-2026-34531 MEDIUM

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

Vendor Miguelgrinberg
Product Flask-HTTPAuth
Weakness CWE-287 · Improper authentication
Published April 1, 2026
Last update May 28, 2026

CVSS base score

6.5/10
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Confidentiality Low
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 1, 2026 CVE published
May 28, 2026 Record updated