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CVE-2026-86253— h3 before 1.15.6 Path Traversal via Percent-Encoded Dot Segments

Quick assessment

Affected
h3js h3
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.

H3是H3组织开源的一个HTTP框架。 H3 2.0.1-rc.14及之前版本存在路径遍历漏洞，该漏洞源于serveStatic()函数未对event.url.pathname进行规范化，导致百分号编码的点段（%2e%2e）经decodeURI()解码为../序列后未进行清理，未经身份验证的远程攻击者可通过发送特制请求读取静态目录之外的任意文件。

CVSS 5.9 · Medium EPSS 0.62% · P49

Affected Version Matrix 4

VendorProduct Version RangeStatus
h3js h3 < 1.15.6 affected
1.15.6 unaffected
2.0.0-beta.0< 2.0.1-rc.15 affected
2.0.1-rc.15 unaffected
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I. Basic Information for CVE-2026-86253

Vulnerability Information
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Vulnerability Title
h3 before 1.15.6 Path Traversal via Percent-Encoded Dot Segments
Source: CVE Program / CVE List V5
Vulnerability Description
h3 (npm package) versions <= 2.0.1-rc.14 contain a path traversal vulnerability in serveStatic(). On Node.js deployments, event.url.pathname is not normalized, so percent-encoded dot segments (%2e%2e) are passed to decodeURI() and decoded to ../ sequences without sanitization. An unauthenticated remote attacker can send crafted requests to endpoints served by serveStatic() to read arbitrary files outside the intended static directory. Fixed in 1.15.6 and 2.0.1-rc.15.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/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
H3 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
H3是H3组织开源的一个HTTP框架。 H3 2.0.1-rc.14及之前版本存在路径遍历漏洞，该漏洞源于serveStatic()函数未对event.url.pathname进行规范化，导致百分号编码的点段（%2e%2e）经decodeURI()解码为../序列后未进行清理，未经身份验证的远程攻击者可通过发送特制请求读取静态目录之外的任意文件。
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
h3js h3 0 ~ 1.15.6 -

II. Public POCs for CVE-2026-86253

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III. Intelligence Information for CVE-2026-86253

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Vendor Advisories for CVE-2026-86253 (2)

Same Patch Batch · h3js · 2026-09-06 · 5 CVEs total

CVE-2026-86250 7.5 HIGH h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie
CVE-2026-86251 5.9 MEDIUM h3 before 1.15.9 Path Traversal via Double Decoding
CVE-2026-86205 5.4 MEDIUM h3 before 2.0.1-rc.18 Open Redirect via redirectBack()
CVE-2026-86252 5.3 MEDIUM h3 before 1.15.9 SSE Event Injection via Carriage Return

IV. Related Vulnerabilities

Same product: h3
Same vendor: h3js
Same weakness: CWE-22

V. Comments for CVE-2026-86253

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