Joris van Rantwijk has reported a vulnerability in Xen, which can be exploited by malicious, local users to gain escalated privileges.

The vulnerability is caused due to an input validation error in tools/pygrub/src/GrubConf.py. This can be exploited by "root" users of a guest domain to execute arbitrary commands in domain 0 via specially crafted entries in grub.conf when the guest system is booted.

The vulnerability is reported in Xen 3.0.3. Other versions may also be affected.

The reported solution is to grant only trusted users "root" privileges to guest domains.

Read the original advisory from Secunia, here.