CVE-2026-34531

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.

Notes

• This issue applies only to token authentication
• This issue applies only when the application verifies tokens by searching for them in a user database.
• This issue applies only if the application stores empty strings as user tokens when the user does not have an assigned token. It does not apply if the application sets those tokens to NULL instead.
• Tokens that are verified through cryptographic means (such as JWTs) are not affected by this issue.
• Basic and Digest authentication are not affected by this issue.

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

CVE-2026-34531 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.8.1); upgrading removes the vulnerable code path.

Kodem intelligence

To protect against this issue, developers should make sure that no user in the user database has their token set to an empty string. If there are such users, change the value of those tokens to NULL instead.

Alternatively, developers can upgrade their projects to Flask-HTTPAuth>=4.8.1, which fixes this issue.

1. What is CVE-2026-34531? CVE-2026-34531 is a medium-severity improper authentication vulnerability in Flask-HTTPAuth (pip), affecting versions <= 4.8.0. It is fixed in 4.8.1. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is CVE-2026-34531? CVE-2026-34531 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of Flask-HTTPAuth are affected by CVE-2026-34531? Flask-HTTPAuth (pip) versions <= 4.8.0 is affected.
4. Is there a fix for CVE-2026-34531? Yes. CVE-2026-34531 is fixed in 4.8.1. Upgrade to this version or later.
5. Is CVE-2026-34531 exploitable, and should I be worried? Whether CVE-2026-34531 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-34531 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-34531? Upgrade Flask-HTTPAuth to 4.8.1 or later.