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CVE-2026-54286— Hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)

Quick assessment

Affected
honojs hono
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.

honojs hono是honojs的Web服务器。 honojs hono 4.12.25之前版本存在路径遍历漏洞，该漏洞源于Windows主机上请求路径中的编码反斜杠（%5C）被解码为\\，导致路径解析器将其视为分隔符，从而使攻击者能够读取本应受前缀挂载中间件保护的静态文件。

CVSS 5.9 · Medium EPSS 0.43% · P35

Affected Version Matrix 1

VendorProduct Version RangeStatus
honojs hono < 4.12.25 affected
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I. Basic Information for CVE-2026-54286

Vulnerability Information
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Vulnerability Title
Hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)
Source: CVE Program / CVE List V5
Vulnerability Description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.25, on Windows hosts, an encoded backslash (%5C) in the request path decodes to \, which the Windows path resolver treats as a separator. serve-static then resolves a single URL segment such as admin\secret.txt into a nested file under the root and serves it, letting an attacker read static files meant to be protected behind prefix-mounted middleware. This vulnerability is fixed in 4.12.25.
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
honojs hono 路径遍历漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
honojs hono是honojs的Web服务器。 honojs hono 4.12.25之前版本存在路径遍历漏洞，该漏洞源于Windows主机上请求路径中的编码反斜杠（%5C）被解码为\\，导致路径解析器将其视为分隔符，从而使攻击者能够读取本应受前缀挂载中间件保护的静态文件。
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
honojs hono < 4.12.25 -

II. Public POCs for CVE-2026-54286

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III. Intelligence Information for CVE-2026-54286

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Vendor Advisories for CVE-2026-54286 (1)

Same Patch Batch · honojs · 2026-06-22 · 5 CVEs total

CVE-2026-54290 7.1 HIGH Hono: CORS Middleware reflects any Origin with credentials when `origin` defaults to the w
CVE-2026-54288 6.5 MEDIUM Hono: Body Limit Middleware can be bypassed on AWS Lambda by understating `Content-Length`
CVE-2026-54287 5.3 MEDIUM Hono: AWS Lambda adapter merges multiple `Set-Cookie` headers into one value, dropping coo
CVE-2026-54289 4.8 MEDIUM Hono: Lambda@Edge adapter keeps only the last value of a repeated request header, dropping

IV. Related Vulnerabilities

Same product: hono
Same vendor: honojs
Same weakness: CWE-22

V. Comments for CVE-2026-54286

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