honojs Hono up to 4.13.15 Mount app.mount improper authorization

Summaryinfo

A vulnerability was found in honojs Hono up to 4.13.15 and classified as problematic. This impacts the function app.mount of the component Mount. The manipulation results in improper authorization. This vulnerability is identified as CVE-2026-126357. The attack can be executed remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in honojs Hono up to 4.13.15. Affected is the function app.mount of the component Mount. The manipulation with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on confidentiality. CVE summarizes:

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.13.16, mount() and app.mount() can remove a dynamic mount prefix using the route-pattern length rather than the matched-prefix length, allowing a crafted path to be forwarded as a protected inner route while the outer application routes the original path. Since 4.12.21, rebuilding the forwarded URL from the decoded pathname can also convert a decoded backslash to a slash and collapse parent-directory segments, again causing the mounted application to receive a protected path. An unauthenticated client can use either applicable path transformation to reach a mounted route without authentication or authorization middleware scoped to a subpath inside the mount prefix. This issue is fixed in version 4.13.16.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-126357 since 11/10/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1548.002 by the MITRE ATT&CK project.

Upgrading to version 4.13.16 eliminates this vulnerability.

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Productinfo

Vendor

• honojs

Name

• Hono

Version

• 4.13.0
• 4.13.1
• 4.13.2
• 4.13.3
• 4.13.4
• 4.13.5
• 4.13.6
• 4.13.7
• 4.13.8
• 4.13.9
• 4.13.10
• 4.13.11
• 4.13.12
• 4.13.13
• 4.13.14
• 4.13.15

Website

• Product: https://github.com/honojs/hono/

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