hono up to 4.9.6 bodyLimit Middleware resource consumption

Summaryinfo

A vulnerability was found in hono up to 4.9.6 and classified as problematic. This affects an unknown function of the component bodyLimit Middleware. Executing a manipulation can lead to resource consumption. This vulnerability is tracked as CVE-2025-59139. The attack can be launched remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in hono up to 4.9.6. It has been declared as problematic. This vulnerability affects an unknown code of the component bodyLimit Middleware. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. CVE summarizes:

Hono is a Web application framework that provides support for any JavaScript runtime. In versions prior to 4.9.7, a flaw in the `bodyLimit` middleware could allow bypassing the configured request body size limit when conflicting HTTP headers were present. The middleware previously prioritized the `Content-Length` header even when a `Transfer-Encoding: chunked` header was also included. According to the HTTP specification, `Content-Length` must be ignored in such cases. This discrepancy could allow oversized request bodies to bypass the configured limit. Most standards-compliant runtimes and reverse proxies may reject such malformed requests with `400 Bad Request`, so the practical impact depends on the runtime and deployment environment. If body size limits are used as a safeguard against large or malicious requests, this flaw could allow attackers to send oversized request bodies. The primary risk is denial of service (DoS) due to excessive memory or CPU consumption when handling very large requests. The implementation has been updated to align with the HTTP specification, ensuring that `Transfer-Encoding` takes precedence over `Content-Length`. The issue is fixed in Hono v4.9.7, and all users should upgrade immediately.

The advisory is available at github.com. This vulnerability was named CVE-2025-59139 since 09/09/2025. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

Upgrading to version 4.9.7 eliminates this vulnerability. Applying the patch 605c70560b52f13af10379f79b76717042fafe8d is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• hono

Version

• 4.9.0
• 4.9.1
• 4.9.2
• 4.9.3
• 4.9.4
• 4.9.5
• 4.9.6

License

• open-source

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