GHSA-wwfh-h76j-fc44

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GHSA-wwfh-h76j-fc44

Summary: hono: Path traversal in `serve-static` on Windows via encoded backslash (`%5C`)

Details: ### 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.

References: https://github.com/honojs/hono/security/advisories/GHSA-wwfh-h76j-fc44, https://nvd.nist.gov/vuln/detail/CVE-2026-54286, https://github.com/honojs/hono