Vulnerability details

### Summary The content of files outside `server.fs` setting can be returned to the browser if the project imports a file path concatenated with the `root`. For example, if the project references `<path-to-project-root>/etc/hosts`, the content of `/etc/hosts` was possible to be returned. The content of files outside the `server.fs.allow` option can be returned to the browser when a project imports a file whose root-relative path matches an absolute path on the host. For example, referencing `<project-root>/etc/hosts` could make Vite return the host's `/etc/hosts` file. ### Impact Only apps that meet all of the following conditions are affected: - explicitly expose the Vite dev server to the network (using `--host` or the [`server.host` option](https://vite.dev/config/server-options#server-host)) - contain an imported file whose root-relative browser URL is also the absolute path of a readable file on the host - The sensitive file is not matched by [`server.fs.deny`](https://vite.dev/config/server-options#server-fs-deny) - the dev server is not running on Windows ### Details When Vite analyzes an in-root import, it rewrites the resolved module ID to a browser URL such as `/etc/hostname`. In affected versions, Vite converts that URL with `fsPathFromUrl` and adds the result to `safeModulePaths`. Because `fsPathFromUrl` ensures a leading slash without resolving the URL against the project root, the project URL `/etc/hostname` is recorded as if it were the absolute filesystem path `/etc/hostname`. For a later request to `/@fs/etc/hostname`, the raw-filesystem middleware interprets `/etc/hostname` as an absolute path. The access check applies `server.fs.deny`, then accepts paths present in `safeModulePaths` before checking `server.fs.allow`. As a result, the request can return the host file instead of the project file that originally populated `safeModulePaths`. ### PoC The following example requires Linux with a readable `/etc/hostname`: ```bash $ mkdir vite-safe-module-path-poc $ cd vite-safe-module-path-poc $ npm init -y $ npm install vite@8.3.1 $ mkdir -p etc $ echo 'PROJECT-DECOY\n' > etc/hostname $ echo 'import "./etc/hostname"\n' > main.js $ npx vite --host 127.0.0.1 ``` In another terminal: ```bash $ curl -o /dev/null -s -w '%{http_code}\n' http://127.0.0.1:5173/main.js 200 $ curl -sS -o response -w '%{http_code}\n' http://127.0.0.1:5173/@fs/etc/hostname 200 $ cmp -s response /etc/hostname && echo 'response matches host file' response matches host file ```