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CVE-2026-6321— fast-uri vulnerable to path traversal via percent-encoded dot segments

Quick assessment

Affected
fast-uri fast-uri
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.

fast-uri是Fastify开源的一个无依赖的RFC 3986 URI解析与工具箱。 fast-uri 3.1.0及之前版本存在路径遍历漏洞，该漏洞源于normalize()和equal()函数在应用点段移除之前解码百分比编码的路径分隔符和点段，编码的路径数据被视为真实斜杠和父目录引用，导致不同URI可能折叠到相同规范化路径，可能绕过基于路径的策略。

CVSS 7.5 · High EPSS 0.63% · P51

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
fast-uri fast-uri < 3.1.1 affected
3.1.1 unaffected
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I. Basic Information for CVE-2026-6321

Vulnerability Information
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Vulnerability Title
fast-uri vulnerable to path traversal via percent-encoded dot segments
Source: CVE Program / CVE List V5
Vulnerability Description
fast-uri decoded percent-encoded path separators and dot segments before applying dot-segment removal in its normalize() and equal() functions. Encoded path data was treated like real slashes and parent-directory references, so distinct URIs could collapse onto the same normalized path. Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed, with a path that appears confined under an allowed prefix normalizing to a different location. Versions <= 3.1.0 are affected. Update to 3.1.1 or later.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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
fast-uri 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
fast-uri是Fastify开源的一个无依赖的RFC 3986 URI解析与工具箱。 fast-uri 3.1.0及之前版本存在路径遍历漏洞，该漏洞源于normalize()和equal()函数在应用点段移除之前解码百分比编码的路径分隔符和点段，编码的路径数据被视为真实斜杠和父目录引用，导致不同URI可能折叠到相同规范化路径，可能绕过基于路径的策略。
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
fast-uri fast-uri 0 ~ 3.1.1 -

II. Public POCs for CVE-2026-6321

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III. Intelligence Information for CVE-2026-6321

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Vendor Advisories for CVE-2026-6321 (1)

IV. Related Vulnerabilities

Same product: fast-uri
Same vendor: fast-uri
Same weakness: CWE-22