CVE-2026-33804— @fastify/middie vulnerable to middleware bypass via deprecated ignoreDuplicateSlashes option
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I. Basic Information for CVE-2026-33804
Vulnerability Information
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Vulnerability Title
@fastify/middie vulnerable to middleware bypass via deprecated ignoreDuplicateSlashes option
Source: NVD (National Vulnerability Database)
Vulnerability Description
@fastify/middie versions 9.3.1 and earlier are vulnerable to middleware bypass when the deprecated Fastify ignoreDuplicateSlashes option is enabled. The middleware path matching logic does not account for duplicate slash normalization performed by Fastify's router, allowing requests with duplicate slashes to bypass middleware authentication and authorization checks. This only affects applications using the deprecated ignoreDuplicateSlashes option. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds other than disabling the ignoreDuplicateSlashes option.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
解释冲突
Source: NVD (National Vulnerability Database)
Vulnerability Title
@fastify/middie 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
@fastify/middie是Fastify开源的一个中间件引擎。 @fastify/middie 9.3.1及之前版本存在安全漏洞，该漏洞源于当启用已弃用的ignoreDuplicateSlashes选项时，中间件路径匹配逻辑未考虑Fastify路由器的重复斜杠规范化，可能导致带有重复斜杠的请求绕过中间件身份验证和授权检查。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| @fastify/middie | @fastify/middie | 0 ~ 9.3.2 | - |
II. Public POCs for CVE-2026-33804
| # | POC Description | Source Link | Shenlong Link |
|---|
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