The openbyhandleat function in vzkernel before 042stab090.5 in the OpenVZ modification for the Linux kernel 2.6.32, when using simfs, might allow local container users with CAPDACREADSEARCH capability to bypass an intended container protection mechanism and access arbitrary files on a filesystem via vectors related to use of the filehandle structure.
vzctl before 4.9.4 determines the virtual environment (VE) layout based on the presence of root.hdd/DiskDescriptor.xml in the VE private directory, which allows local simfs container (CT) root users to change the root password for arbitrary ploop containers, as demonstrated by a symlink attack on the ploop container root.hdd file and then access a control panel.