Authentication bypass via empty token callback
Published Apr 1, 2026 · Updated Apr 1, 2026
Improper authentication in Flask-HTTPAuth before 4.8.1 allows remote attackers to access protected routes with an empty token. HTTPTokenAuth.authenticate passes a missing or empty token to the application's verification callback instead of rejecting the request. Exploitation requires token authentication, database-backed token lookup, and at least one user whose stored token is an empty string; Basic, Digest, JWT, and NULL-token configurations are unaffected.
Summary
What happened
Improper authentication in Flask-HTTPAuth before 4.8.1 allows remote attackers to access protected routes with an empty token. HTTPTokenAuth.authenticate passes a missing or empty token to the application's verification callback instead of rejecting the request. Exploitation requires token authentication, database-backed token lookup, and at least one user whose stored token is an empty string; Basic, Digest, JWT, and NULL-token configurations are unaffected.
The record
- CVE
- CVE-2026-34531
- Published
- Apr 1, 2026
- Updated
- Apr 1, 2026
- Vendor
- Miguel Grinberg
- Product
- Flask-HTTPAuth
- Classifications
- CWE-287, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 1, 2026CVE publishedPublication date reported by the CVE source.
- Apr 1, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=< 4.8.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
Your stack
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Your stack
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