CVE-2026-39406
@hono/node-server: Middleware bypass via repeated slashes in serveStatic
Description
## Summary 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. ## Details The routing layer and `serveStatic` handle repeated slashes differently. For example: - `/admin/secret.txt` => matches `/admin/*` - `//admin/secret.txt` => may not match `/admin/*` This inconsistency allows a request such as: ``` GET //admin/secret.txt ``` to bypass middleware registered on `/admin/*` and access protected files. ## Impact An attacker can access static files that are intended to be protected by route-based middleware by using repeated slashes in the request path. This can lead to unauthorized access to sensitive files under the static root. This issue affects applications that rely on `serveStatic` together with route-based middleware for access control.
How to fix CVE-2026-39406
To remediate CVE-2026-39406, upgrade the affected package to a fixed version below.
- —upgrade to 1.19.13 or later
Is CVE-2026-39406 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 1.19.13
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N |