diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
index 958f58e2a0179..695d4a3357fa8 100644
--- a/lib/private/Preview/Generator.php
+++ b/lib/private/Preview/Generator.php
@@ -257,9 +257,15 @@ public static function unguardWithSemaphore(false|\SysvSemaphore $semId): bool {
 	 */
 	public static function getHardwareConcurrency(): int {
 		static $width;
+
 		if (!isset($width)) {
-			if (is_file("/proc/cpuinfo")) {
-				$width = substr_count(file_get_contents("/proc/cpuinfo"), "processor");
+			if (function_exists('ini_get')) {
+				$openBasedir = ini_get('open_basedir');
+				if (empty($openBasedir) || strpos($openBasedir, '/proc/cpuinfo') !== false) {
+					$width = is_readable('/proc/cpuinfo') ? substr_count(file_get_contents('/proc/cpuinfo'), 'processor') : 0;
+				} else {
+					$width = 0;
+				}
 			} else {
 				$width = 0;
 			}