CVE-2026-29087

When using @hono/node-server's static file serving together with route-based middleware protections (e.g. protecting /admin/*), inconsistent URL decoding can allow protected static resources to be accessed without authorization.

In particular, paths containing encoded slashes (%2F) may be evaluated differently by routing/middleware matching versus static file path resolution, enabling a bypass where middleware does not run but the static file is still served.

Details

The routing layer and the node-server static handler normalize request paths differently. The router preserves %2F as a literal string when matching routes, while the static handler decodes %2F into / before resolving the filesystem path.

Example request:

• /admin%2Fsecret.html

This may:

• fail to match middleware intended for /admin/*, but
• still be resolved by the static handler as /admin/secret.html under the configured static root.

This does not allow access outside the configured static root and is not a path traversal vulnerability.

An unauthenticated attacker could bypass route-based authorization protections for protected static resources by supplying paths containing encoded slashes.

Applications relying solely on route-based middleware to protect static subpaths under the same static root may have exposed those resources.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2026-29087 has a CVSS score of 7.5 (High). 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 (1.19.10); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-29087? CVE-2026-29087 is a high-severity incorrect authorization vulnerability in @hono/node-server (npm), affecting versions < 1.19.10. It is fixed in 1.19.10. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2026-29087? CVE-2026-29087 has a CVSS score of 7.5 (High). 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/node-server are affected by CVE-2026-29087? @hono/node-server (npm) versions < 1.19.10 is affected.
4. Is there a fix for CVE-2026-29087? Yes. CVE-2026-29087 is fixed in 1.19.10. Upgrade to this version or later.
5. Is CVE-2026-29087 exploitable, and should I be worried? Whether CVE-2026-29087 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-2026-29087 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-2026-29087? Upgrade @hono/node-server to 1.19.10 or later.