CVE-2025-59139

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.

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.

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.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2025-59139 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.9.7); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-59139? CVE-2025-59139 is a medium-severity uncontrolled resource consumption vulnerability in hono (npm), affecting versions < 4.9.7. It is fixed in 4.9.7. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2025-59139? CVE-2025-59139 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of hono are affected by CVE-2025-59139? hono (npm) versions < 4.9.7 is affected.
4. Is there a fix for CVE-2025-59139? Yes. CVE-2025-59139 is fixed in 4.9.7. Upgrade to this version or later.
5. Is CVE-2025-59139 exploitable, and should I be worried? Whether CVE-2025-59139 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-59139 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-59139? Upgrade hono to 4.9.7 or later.