GHSA-wr4h-v87w-p3r7

## Summary `serveStatic()` in h3 is vulnerable to path traversal via percent-encoded dot segments (`%2e%2e`), allowing an unauthenticated attacker to read arbitrary files outside the intended static directory on Node.js deployments. ## Details The vulnerability exists in `src/utils/static.ts` at [line 86](https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/static.ts#L86): ```typescript const originalId = decodeURI(withLeadingSlash(withoutTrailingSlash(event.url.pathname))); ``` On Node.js, h3 uses srvx's `FastURL` class to parse request URLs. Unlike the standard WHATWG `URL` parser, `FastURL` extracts the pathname via raw string slicing for performance — it does **not** normalize dot segments (`.` / `..`) or resolve percent-encoded equivalents (`%2e`). This means a request to `/%2e%2e/` will have `event.url.pathname` return `/%2e%2e/` verbatim, whereas the standard `URL` parser would normalize it to `/` (resolving `..` upward). The `serveStatic()` function then calls `decodeURI()` on this raw pathname, which decodes `%2e` to `.`, producing `/../`. The resulting path containing `../` traversal sequences is passed directly to the user-provided `getMeta()` and `getContents()` callbacks with no sanitization or traversal validation. When these callbacks perform filesystem operations (the intended and documented usage), the `../` sequences resolve against the filesystem, escaping the static root directory. Before exploit: <img width="761" height="97" alt="image" src="https://github.com/user-attachments/assets/798f9d3d-f76c-4c29-aca3-5a6ccd3b3627" /> ### Vulnerability chain ``` 1. Attacker sends: GET /%2e%2e/%2e%2e/%2e%2e/etc/passwd 2. FastURL.pathname: /%2e%2e/%2e%2e/%2e%2e/etc/passwd (raw, no normalization) 3. decodeURI(): /../../../etc/passwd (%2e decoded to .) 4. getMeta(id): id = "/../../../etc/passwd" (no traversal check) 5. path.join(root,id): /etc/passwd (.. r