@fastify/express vulnerable to Improper Handling of URL Encoding (Hex Encoding)

The @fastify/express plugin adds full Express compatibility to Fastify. A security vulnerability exists in @fastify/express prior to version 4.0.3 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. The vulnerability is caused by how @fastify/express matches requests against registered middleware paths. This vulnerability is similar to, but differs from, CVE-2026-22031 because this is a different npm module with its own code. Version 4.0.3 of @fastify/express contains a patch fort the issue.

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

URL编码处理不恰当(Hex编码)

@fastify/express 安全漏洞

@fastify/express是Fastify开源的一个兼容性插件。 @fastify/express 4.0.3之前版本存在安全漏洞，该漏洞源于路径前缀匹配不当，可能导致中间件绕过。

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