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Hono has Body Limit Middleware Bypass

Moderate severity GitHub Reviewed Published Sep 12, 2025 in honojs/hono • Updated Sep 12, 2025

Package

npm hono (npm)

Affected versions

< 4.9.7

Patched versions

4.9.7

Description

Summary

A flaw in the bodyLimit middleware could allow bypassing the configured request body size limit when conflicting HTTP headers were present.

Details

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.

Impact

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.

Resolution

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.

References

@yusukebe yusukebe published to honojs/hono Sep 12, 2025
Published by the National Vulnerability Database Sep 12, 2025
Published to the GitHub Advisory Database Sep 12, 2025
Reviewed Sep 12, 2025
Last updated Sep 12, 2025

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS score

Weaknesses

Uncontrolled Resource Consumption

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. Learn more on MITRE.

Allocation of Resources Without Limits or Throttling

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Learn more on MITRE.

CVE ID

CVE-2025-59139

GHSA ID

GHSA-92vj-g62v-jqhh

Source code

Credits

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