CVE-2026-39407

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path. When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass. This vulnerability is fixed in 4.12.12.

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path. When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass. This vulnerability is fixed in 4.12.12.

Summary

A path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path.

When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass.

Details

The routing layer and serveStatic handle repeated slashes differently.

For example:

/admin/secret.txt => matches /admin/*
/admin//secret.txt => may not match /admin/*

However, serveStatic may interpret both paths as the same file location (e.g., admin/secret.txt) and return the file.

This inconsistency allows a request such as:

GET //admin/secret.txt

to bypass middleware registered on /admin/* and access protected files.

The issue has been fixed by rejecting paths that contain repeated slashes, ensuring consistent behavior between route matching and static file resolution.

Impact

An attacker can access static files that are intended to be protected by route-based middleware by using repeated slashes in the request path.

This can lead to unauthorized access to sensitive files under the static root.

This issue affects applications that rely on serveStatic together with route-based middleware for access control.

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path. When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass. This vulnerability is fixed in 4.12.12.

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, a path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path. When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass. This vulnerability is fixed in 4.12.12.

Summary

A path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path.

When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass.

Details

The routing layer and serveStatic handle repeated slashes differently.

For example:

/admin/secret.txt => matches /admin/*
/admin//secret.txt => may not match /admin/*

However, serveStatic may interpret both paths as the same file location (e.g., admin/secret.txt) and return the file.

This inconsistency allows a request such as:

GET //admin/secret.txt

to bypass middleware registered on /admin/* and access protected files.

The issue has been fixed by rejecting paths that contain repeated slashes, ensuring consistent behavior between route matching and static file resolution.

Impact

An attacker can access static files that are intended to be protected by route-based middleware by using repeated slashes in the request path.

This can lead to unauthorized access to sensitive files under the static root.

This issue affects applications that rely on serveStatic together with route-based middleware for access control.

Root has patched CVE-2026-39407 in the hono package for Root:npm. Multiple fixed versions available.

TuxCare rebuilt hono to address 15 CVEs. Fixed in 3.12.12-tuxcare.1.