vzctl: Security bypass

Background

vzctl is a set of control tools for the OpenVZ server virtualization solution.

Description

It was discovered that vzctl determined the virtual environment (VE) layout based on the presence of root.hdd/DiskDescriptor.xml in the VE private directory. This allows local simfs container (CT) root users to change the root password for arbitrary ploop containers. This is demonstrated by a symlink attack on the ploop container root.hdd file which can then be used to access a control panel.

Impact

An attacker with root privileges, in a simfs-based container, could gain control over ploop-based containers.

Workaround

There is no known workaround at this time.

Resolution

All vzctl users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=sys-cluster/vzctl-4.9.4"