Unauthenticated authorization bypass via encoded path slash
Published Jul 1, 2026 · Updated Jul 1, 2026
Authorization bypass in Fastify @fastify/middie 9.1.0 through 9.3.2 allows remote attackers to reach protected route handlers. Middleware path matching decodes %2F inside parameter values while Fastify route lookup preserves it, so a crafted URL skips the middleware but matches the handler. Exploitation requires a parameterized middleware path used for a security decision; no authentication, special precondition, or user interaction is required.
Summary
What happened
Authorization bypass in Fastify @fastify/middie 9.1.0 through 9.3.2 allows remote attackers to reach protected route handlers. Middleware path matching decodes %2F inside parameter values while Fastify route lookup preserves it, so a crafted URL skips the middleware but matches the handler. Exploitation requires a parameterized middleware path used for a security decision; no authentication, special precondition, or user interaction is required.
The record
- CVE
- CVE-2026-14198
- Published
- Jul 1, 2026
- Updated
- Jul 1, 2026
- Vendor
- Fastify
- Product
- @fastify/middie
- Classifications
- CWE-436, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 1, 2026CVE publishedPublication date reported by the CVE source.
- Jul 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=9.1.0 <9.3.3
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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