Two vulnerabilities have been reported in Xen, which can be exploited by malicious, local users in a guest virtual machine to cause a DoS (Denial of Service) and gain escalated privileges.

1) An error when handling certain system calls can be exploited to gain additional privileges.

Successful exploitation of this vulnerability requires a 64-bit PV guest kernel running on a 64-bit hypervisor.

2) An error when handling exceptions does not properly clear a flag, which can be exploited to cause a crash.

Note: This vulnerability does not affect HVM guests.

The vulnerabilities are reported in versions 3.4, 4.0, and 4.1.

Note: Additionally, a weakness exists within 64-bit PV guests, which can lead to CPU lock ups.

Solution
Apply patches (please see the vendor's advisory for more information).

Provided and/or discovered by
1) The vendor credits Rafal Wojtczuk.
2) Reported by the vendor.

Original Advisory
XSA-7:
http://lists.xen.org/archives/html/xen-announce/2012-06/msg00001.html

XSA-8:
http://lists.xen.org/archives/html/xen-announce/2012-06/msg00003.html

XSA-9:
http://lists.xen.org/archives/html/xen-announce/2012-06/msg00002.html

Deep Links
Links available to Secunia VIM customers