Index: wp-includes/functions.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- wp-includes/functions.php	(revision 39820)
+++ wp-includes/functions.php	(revision )
@@ -2377,6 +2377,17 @@
 		$mime = false;
 	}
 
+	try {
+        if ( false === $mime && function_exists( 'finfo_file' ) ) {
+            // Use finfo_file if available to validate non-image files.
+            $finfo = finfo_open( FILEINFO_MIME_TYPE );
+            $mime = finfo_file( $finfo, $file );
+            finfo_close( $finfo );
+        }
+    } catch ( Exception $e ) {
+	    $mime = false;
+    }
+
 	return $mime;
 }