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CVE-2026-18427— @fastify/static vulnerable to route guard bypass via non-canonical path segments

Quick assessment

Affected
@fastify/static @fastify/static
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Fastify @fastify/static是Fastify组织的一款提供静态文件服务的插件。 Fastify @fastify/static 10.1.3之前版本存在安全漏洞，该漏洞源于之前路由守卫绕过的修复不完整，未规范化点段、重复斜杠、编码点或反斜杠，可能导致未认证攻击者使用非规范路径形式请求受路由守卫保护的文件，泄露其内容。

CVSS 7.5 · High EPSS 0.43% · P37

Affected Version Matrix 2

VendorProduct Version RangeStatus
@fastify/static @fastify/static < 10.1.3 affected
10.1.3 unaffected
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I. Basic Information for CVE-2026-18427

Vulnerability Information
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Vulnerability Title
@fastify/static vulnerable to route guard bypass via non-canonical path segments
Source: CVE Program / CVE List V5
Vulnerability Description
@fastify/static before version 10.1.3 contains an incomplete fix for a previous route guard bypass. The static file handler rejected only parent directory segments, but it did not canonicalize dot segments, duplicate slashes, encoded dots, or backslashes before route matching and before delegating to the send layer. As a result, an unauthenticated attacker could request a file protected by a route based guard using a non canonical path form that misses the guarded route yet resolves back onto the protected file, disclosing its contents. Applications that protect a subtree of the static root with a route based guard are affected, while applications relying on the allowedPath option are not. This is fixed in @fastify/static 10.1.3, which canonicalizes the pathname, including rejecting backslashes, on the path used for routing and serving.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5
Vulnerability Title
Fastify @fastify/static 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Fastify @fastify/static是Fastify组织的一款提供静态文件服务的插件。 Fastify @fastify/static 10.1.3之前版本存在安全漏洞，该漏洞源于之前路由守卫绕过的修复不完整，未规范化点段、重复斜杠、编码点或反斜杠，可能导致未认证攻击者使用非规范路径形式请求受路由守卫保护的文件，泄露其内容。
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/static @fastify/static 0 ~ 10.1.3 -

II. Public POCs for CVE-2026-18427

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III. Intelligence Information for CVE-2026-18427

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Vendor Advisories for CVE-2026-18427 (1)

IV. Related Vulnerabilities

Same product: @fastify/static
Same vendor: @fastify/static
Same weakness: CWE-22

V. Comments for CVE-2026-18427

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