(RHSA-2012:1236) Important: xen security update

The xen packages contain administration tools and the xend service for
managing the kernel-xen kernel for virtualization on Red Hat Enterprise
Linux.

A flaw was found in the way QEMU handled VT100 terminal escape sequences
when emulating certain character devices. A guest user with privileges to
write to a character device that is emulated on the host using a virtual
console back-end could use this flaw to crash the qemu process on the
host or, possibly, escalate their privileges on the host. (CVE-2012-3515)

This flaw did not affect the default use of the Xen hypervisor
implementation in Red Hat Enterprise Linux 5. This problem only affected
fully-virtualized guests that have a serial or parallel device that uses a
virtual console (vc) back-end. By default, the virtual console back-end is
not used for such devices; only guests explicitly configured to use them
in this way were affected.

Red Hat would like to thank the Xen project for reporting this issue.

All users of xen are advised to upgrade to these updated packages, which
correct this issue. After installing the updated packages, all
fully-virtualized guests must be restarted for this update to take effect.