# GHSA-frvp-7c67-39w9: Node.js Adapter for Hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)

> Unauthenticated attackers can read protected static files on Windows hosts by using encoded backslashes to bypass middleware guards in the Hono Node.js adapter.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Jul 2026

## What is GHSA-frvp-7c67-39w9?

GHSA-frvp-7c67-39w9 is a path traversal vulnerability in @hono/node-server, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The same as the `hono` core [Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)](https://github.com/honojs/hono/security/advisories/GHSA-wwfh-h76j-fc44).

### Summary

On Windows hosts, an encoded backslash (`%5C`) in the request path decodes to `\`, which the Windows path resolver treats as a separator. `serve-static` then resolves a single URL segment such as `admin\secret.txt` into a nested file under the root and serves it, letting an attacker read static files meant to be protected behind prefix-mounted middleware. Directory escape (`..`) remains blocked.

### Details

The router splits paths only on `/`, so `/admin%5Csecret.txt` is one segment and middleware on `/admin/*` does not run. The `serve-static` guard rejects `.`/`..` and consecutive separators but lets a lone `\` through; on Windows the file resolver re-splits it into the protected subtree.

This affects Windows hosts serving static files via the Node, Bun, or Deno adapters that guard a static subtree with prefix-mounted middleware.

### Impact

An unauthenticated attacker can read static files under a middleware-guarded prefix on Windows hosts. The read stays within the configured root; escape outside the root is not possible.

## Which versions are affected by GHSA-frvp-7c67-39w9?

4 open source packages ship an affected version, including @hono/node-server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@hono/node-server` | npm | All versions | 1.19.15 |
| `@hono/node-server` | npm | All versions | 1.19.15 |
| `@hono/node-server` | npm | From 2.0.0 | 2.0.5 |
| `@hono/node-server` | npm | From 2.0.0 | 2.0.5 |

## How do I fix GHSA-frvp-7c67-39w9?

Upgrade @hono/node-server to a fixed version for your release line: 1.19.15 or 2.0.5.

## Is GHSA-frvp-7c67-39w9 being exploited?

There is no known exploitation of GHSA-frvp-7c67-39w9 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-frvp-7c67-39w9 and fix it if it is affected.

What it is: GHSA-frvp-7c67-39w9 is a path traversal vulnerability in @hono/node-server, published on 21 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-frvp-7c67-39w9 in the wild and no public exploit code.

Affected packages and fixed versions:
- @hono/node-server (npm): affected all versions; fixed in 1.19.15
- @hono/node-server (npm): affected all versions; fixed in 1.19.15
- @hono/node-server (npm): affected from 2.0.0; fixed in 2.0.5
- @hono/node-server (npm): affected from 2.0.0; fixed in 2.0.5

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/GHSA-frvp-7c67-39w9/ (Markdown: https://insights.sbomify.com/GHSA-frvp-7c67-39w9/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-frvp-7c67-39w9

---
From sbomify Insights: https://insights.sbomify.com/GHSA-frvp-7c67-39w9/
Summaries are generated and may contain mistakes; the official description above is the record.