CVE-2026-28492

### Summary When a user creates a public share link for a **directory**, the `withHashFile` middleware in `http/public.go` (line 59) uses `filepath.Dir(link.Path)` to compute the `BasePathFs` root. This sets the filesystem root to the **parent directory** instead of the shared directory itself, allowing anyone with the share link to browse and download files from all sibling directories. ### Details In `http/public.go` lines 52-64, the `withHashFile` function handles public share link requests: ```go basePath := link.Path // e.g. "/documents/shared" filePath := "" if file.IsDir { basePath = filepath.Dir(basePath) // BUG: becomes "/documents" (parent!) filePath = ifPath } d.user.Fs = afero.NewBasePathFs(d.user.Fs, basePath) ``` When a directory at `/documents/shared` is shared, `filepath.Dir("/documents/shared")` evaluates to `"/documents"`. The `BasePathFs` is then rooted at the parent directory `/documents/`, giving the share link access to **everything** under `/documents/` - not just the intended `/documents/shared/`. This affects both `publicShareHandler` (directory listing via `/api/public/share/{hash}`) and `publicDlHandler` (file download via `/api/public/dl/{hash}/path`). ### PoC 1. Set up filebrowser with a user whose scope contains: 2. - `/documents/shared/public-file.txt` (intended to be shared) 3. - `/documents/secrets/passwords.txt` (NOT intended to be shared) 4. - `/documents/private/financial.csv` (NOT intended to be shared) 2. Create a public share link for the directory `/documents/shared` (via POST `/api/share/documents/shared`) 3. Access the share link: `GET /api/public/share/{hash}` 4. - **Expected**: Lists only contents of `/documents/shared/` 5. - **Actual**: Lists contents of `/documents/` (parent), revealing `secrets/`, `private/`, and `shared/` directories 4. Download sibling files: `GET /api/public/dl/{hash}/secrets/passwords.txt` 5. - **Expected**: 404 or 403 (file outside share scope) 6. - **Actual**: 200 with file contents (sibling file downloaded successfully) **Standalone Go test** reproducing the exact vulnerable code path with `afero.NewBasePathFs`: ```go func TestShareScopeEscape(t *testing.T) { baseFs := afero.NewMemMapFs() afero.WriteFile(baseFs, "/documents/shared/public.txt", []byte("public"), 0644) afero.WriteFile(baseFs, "/documents/secrets/passwords.txt", []byte("admin:hunter2"), 0644) linkPath := "/documents/shared" basePath := filepath.Dir(linkPath) // BUG: "/documents" scopedFs := afero.NewBasePathFs(baseFs, basePath) // Sibling file is accessible through the share: f, err := scopedFs.Open("/secrets/passwords.txt") // err is nil - file accessible! Content: "admin:hunter2" } ``` This test passes, confirming the vulnerability. ### Impact **Unauthenticated information disclosure (CWE-200, CWE-706)**. Anyone with a public share link for a directory can: - Browse all sibling directories and files of the shared directory - - Download any file within the parent directory scope - - This works without authentication (public shares) or after providing the share password (password-protected shares) All filebrowser v2.x installations that use directory sharing are affected. ### Recommended Fix Remove the `filepath.Dir()` call and use `link.Path` directly as the `BasePathFs` root: ```go if file.IsDir { // Don't change basePath - keep it as link.Path filePath = ifPath } d.user.Fs = afero.NewBasePathFs(d.user.Fs, basePath) ``` **Affected commit**: e3d00d591b567a8bfe3b02e42ba586859002c77d (latest) **File**: `http/public.go`, line 59

FileBrowser has Path Traversal in Public Share Links that Exposes Files Outside Shared Directory in github.com/filebrowser/filebrowser