Adminer has an Unauthenticated Persistent DoS via Array Injection in ?script=version Endpoint

Summary

Adminer v5.4.1 has a version check mechanism where adminer.org sends signed version info via JavaScript postMessage, which the browser then POSTs to ?script=version. This endpoint lacks origin validation and accepts POST data from any source. An attacker can POST version[] parameter which PHP converts to an array. On next page load, openssl_verify() receives this array instead of string and throws TypeError, returning HTTP 500 to all users.

Fix

Upgrade to Adminer 5.4.2.

Mitigation (if you can't upgrade): Make file adminer.version in temp directory (usually the value of upload_tmp_dir) unwritable by web server.

Details

1. Intended design of ?script=version:

The endpoint is designed to receive version data from adminer.org via browser JavaScript:

• functions.js line 102-117: Creates iframe to https://www.adminer.org/version/
• Adminer.org sends signed version data via postMessage
• JavaScript POSTs this to ?script=version
• Server stores in /tmp/adminer.version for signature verification

// functions.js line 117
ajax(url + 'script=version', () => { }, event.data + '&token=' + token);

2. The vulnerability:

The endpoint only checks $_GET["script"] == "version" - it does not validate:

• Request origin (no CSRF token check for this endpoint)
• Request source (any HTTP client can POST)
• Parameter types (version expected as string, array not rejected)

// bootstrap.inc.php line 32-40
if ($_GET["script"] == "version") {
    $filename = get_temp_dir() . "/adminer.version";
    @unlink($filename);
    $fp = file_open_lock($filename);
    if ($fp) {
        file_write_unlock($fp, serialize(array("signature" => $_POST["signature"], "version" => $_POST["version"])));
    }
    exit;
}

3. Type confusion crash:

When POST contains version[] instead of version, PHP creates an array. When Adminer reads this file and passes to openssl_verify():