honojs hono up to 4.12.20 app.mount request smuggling

Summaryinfo

A vulnerability has been found in honojs hono up to 4.12.20 and classified as problematic. This affects the function app.mount. The manipulation leads to request smuggling. This vulnerability is listed as CVE-2026-47676. The attack may be initiated remotely. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in honojs hono up to 4.12.20. It has been rated as problematic. This issue affects the function app.mount. The manipulation with an unknown input leads to a request smuggling vulnerability. Using CWE to declare the problem leads to CWE-444. The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. Impacted is confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-47676 since 05/19/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 4.12.21 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• honojs

Name

• hono

Version

• 4.12.0
• 4.12.1
• 4.12.2
• 4.12.3
• 4.12.4
• 4.12.5
• 4.12.6
• 4.12.7
• 4.12.8
• 4.12.9
• 4.12.10
• 4.12.11
• 4.12.12
• 4.12.13
• 4.12.14
• 4.12.15
• 4.12.16
• 4.12.17
• 4.12.18
• 4.12.19
• 4.12.20

Website

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

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion