GHSA-wwpw-hrx8-79r5 AVideo: Unauthenticated File Deletion via PHP Operator Precedence Bug in CLI Guard

• Packagist wwbn/avideo: <= 26.0 (no fix yet)

Summary The AVideo installation script `install/deleteSystemdPrivate.php` contains a PHP operator precedence bug in its CLI-only access guard. The script is intended to run exclusively from the command line, but the guard condition `!php_sapi_name() === 'cli'` never evaluates to true due to how PHP resolves operator precedence. The `!` (logical NOT) operator binds more tightly than `===` (strict comparison), causing the expression to always evaluate to `false`, which means the `die()` statement never executes. As a result, the script is accessible via HTTP without authentication and will delete files from the server's temp directory while also disclosing the temp directory contents in its response. Details The faulty guard is at lines 2-4 of the script: ```php // install/deleteSystemdPrivate.php:2-4 if (!php_sapi_name() === 'cli') { die('Command Line only'); } ``` Due to PHP operator precedence, this expression is parsed as: ```php if ((!php_sapi_name()) === 'cli') { ``` Step-by-step evaluation when accessed via HTTP (Apache/nginx with mod_php or php-fpm): 1. `php_sapi_name()` returns `"apache2handler"` (or `"fpm-fcgi"`, etc.) - a non-empty string 2. `!php_sapi_name()` applies logical NOT to a truthy string, yielding `false` 3. `false === 'cli'` is a strict comparison between a boolean and a string, which is always `false` 4. The `if` body (`die()`) is never entered The correct code should be: ```php if (php_sapi_name() !== 'cli') { die('Command Line only'); } ``` After the bypassed guard, the script enumerates and deletes aged files from the system temp directory: ```php $glob = glob(sys_get_temp_dir() . "/*"); // ... foreach ($glob as $file) { if (filemtime($file) ``` Step 3: Monitor the effect by checking before and after: ```bash Check initial state curl -s "https://your-avideo-instance.com/install/deleteSystemdPrivate.php" | head -1 Output: "Found total of 91 items" Wait and check again - files older than 24 hours will have been deleted curl -s "https://your-avideo-instance.com/install/deleteSystemdPrivate.php" | head -1 Output: "Found total of 47 items" (fewer items after deletion) ``` Impact An unauthenticated attacker can trigger deletion of files in the server's system temp directory by simply sending an HTTP request to this endpoint. The impact includes: • File deletion: Any files in the temp directory older than 24 hours are deleted. This can disrupt server operations by removing PHP session files, upload temp files, cache files, or files used by other applications sharing the same temp directory. • Information disclosure: The script's output reveals the full path of the temp directory and enumerates its contents, including file names and counts. This can expose internal server paths, session file names, and the presence of other applications. • Denial of service: Repeated requests can be used to continuously purge temp files, interfering with file uploads, session management, and other temp-dependent operations. The root cause is a common PHP pitfall where the logical NOT operator (`!`) has higher precedence than strict comparison (`===`), causing the intended CLI-only guard to be completely ineffective. • CWE-284: Improper Access Control • Severity: Medium Recommended Fix Fix the operator precedence bug at `install/deleteSystemdPrivate.php:2` by replacing the negation with the `!==` operator: ```php // install/deleteSystemdPrivate.php:2 // Before (broken - always evaluates to false): if (!php_sapi_name() === 'cli') { // After (correct): if (php_sapi_name() !== 'cli') { ``` --- *Found by aisafe.io*