@fastify/middie is the plugin that adds middleware support on steroids to Fastify. A security vulnerability exists in @fastify/middie prior to version 9.1.0 where middleware registered with a specific path prefix can be bypassed using URL-encoded characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. Version 9.1.0 fixes the issue.
Metrics
Affected Vendors & Products
References
History
Tue, 20 Jan 2026 15:15:00 +0000
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ssvc
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Tue, 20 Jan 2026 08:45:00 +0000
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Fastify
Fastify fastify |
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| Vendors & Products |
Fastify
Fastify fastify |
Mon, 19 Jan 2026 15:45:00 +0000
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| Description | @fastify/middie is the plugin that adds middleware support on steroids to Fastify. A security vulnerability exists in @fastify/middie prior to version 9.1.0 where middleware registered with a specific path prefix can be bypassed using URL-encoded characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. Version 9.1.0 fixes the issue. | |
| Title | Fastify Middie Middleware Path Bypass | |
| Weaknesses | CWE-177 | |
| References |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published: 2026-01-19T15:24:45.899Z
Updated: 2026-01-20T14:45:31.487Z
Reserved: 2026-01-05T22:30:38.718Z
Link: CVE-2026-22031
Updated: 2026-01-20T14:45:24.914Z
Status : Received
Published: 2026-01-19T16:15:54.310
Modified: 2026-01-19T16:15:54.310
Link: CVE-2026-22031
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