CVE-2026-39407: Hono: Middleware bypass via repeated slashes in serveStatic

April 8, 2026

A path handling inconsistency in serveStatic allows protected static files to be accessed by using repeated slashes (//) in the request path.

When route-based middleware (e.g., /admin/*) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass.

References

github.com/advisories/GHSA-wmmm-f939-6g9c
github.com/honojs/hono
github.com/honojs/hono/commit/9aff14bd727f8b0435c963363fd803260e7b8e3c
github.com/honojs/hono/releases/tag/v4.12.12
github.com/honojs/hono/security/advisories/GHSA-wmmm-f939-6g9c
nvd.nist.gov/vuln/detail/CVE-2026-39407

Code Behaviors & Features

Detect and mitigate CVE-2026-39407 with GitLab Dependency Scanning

Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Learn more about Dependency Scanning →