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CVE-2026-47676— Hono: app.mount() strips mount prefix using undecoded path, causing incorrect routing for percent-encoded paths

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.

Hono是Hono社区的一个用 TypeScript 编写的 Web 框架。 Hono 4.12.21之前版本存在安全漏洞，该漏洞源于app.mount()使用原始URL路径名去除挂载前缀，而路由匹配针对百分比解码路径执行，导致当路径包含百分比编码的多字节字符时前缀被错误去除，使挂载的子应用程序接收到错误路径。

CVSS 5.3 · Medium EPSS 0.33% · P24

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
honojs hono < 4.12.21 affected
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I. Basic Information for CVE-2026-47676

Vulnerability Information
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Vulnerability Title
Hono: app.mount() strips mount prefix using undecoded path, causing incorrect routing for percent-encoded paths
Source: CVE Program / CVE List V5
Vulnerability Description
Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.21, app.mount() strips the mount prefix from the incoming request path using the raw URL pathname, while route matching is performed against the percent-decoded path. This inconsistency causes the prefix to be stripped at the wrong position when the path contains percent-encoded multi-byte characters, resulting in the mounted sub-application receiving an incorrect path. This vulnerability is fixed in 4.12.21.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
HTTP请求的解释不一致性(HTTP请求私运)
Source: CVE Program / CVE List V5
Vulnerability Title
Hono 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Hono是Hono社区的一个用 TypeScript 编写的 Web 框架。 Hono 4.12.21之前版本存在安全漏洞，该漏洞源于app.mount()使用原始URL路径名去除挂载前缀，而路由匹配针对百分比解码路径执行，导致当路径包含百分比编码的多字节字符时前缀被错误去除，使挂载的子应用程序接收到错误路径。
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 < 4.12.21 -

II. Public POCs for CVE-2026-47676

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III. Intelligence Information for CVE-2026-47676

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Vendor Advisories for CVE-2026-47676 (1)

Same Patch Batch · honojs · 2026-05-28 · 4 CVEs total

CVE-2026-47674 5.3 MEDIUM Hono: IP Restriction bypasses static deny rules for non-canonical IPv6
CVE-2026-47673 4.8 MEDIUM Hono: JWT middleware accepts any Authorization scheme, not only Bearer
CVE-2026-47675 4.3 MEDIUM Hono: Cookie helper does not sanitize sameSite and priority, allowing Set-Cookie injection

IV. Related Vulnerabilities

Same product: hono
Same vendor: honojs
Same weakness: CWE-444

V. Comments for CVE-2026-47676

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