An important bug related to VFS or in memory files was fixed in ColdFusion 11 update 5.
Issue was related to clearing up any in memory files once VFS was disabled. Suppose your app had previously enabled VFS and created few files in memory. Now at any point in time if VFS was disabled these files will still be in memory and were not getting cleared.
With ColdFusion 11 update 5 the same issue has been fixed and VFS files will be cleared as soon as VFS is disabled.
The same fix is also available for ColdFusion 10 update 16.
Refer to bug (https://bugbase.adobe.com/index.cfm?event=bug&id=3039708) for more details on the same.