Some 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 potentially gain escalated privileges.

1) An error when handling writes to the DR7 debug control register can be exploited to cause a crash via the "set_debugreg" hypercall.

2) An error within the "PHYSDEVOP_get_free_pirq" hypercall when allocating a physical IRQ does not properly verify the return value of a call to get_free_pirq.

3) An error within the "XENMEM_populate_physmap" macro when handling certain flags can be exploited to cause a crash via the MEMF_populate_on_demand flag.

4) An array indexing error within "PHYSDEVOP_map_pirq" can be exploited to cause a crash.

5) An error when handling VT100 sequences can be exploited to overwrite portions of the device model's address space and gain escalated privileges.

The vulnerabilities are reported in versions 4.1, 4.0, and 3.4 (please see the vendor's advisory for more information).

Solution
Apply patches (please see the vendor's advisory for more information).
Further details available to Secunia VIM customers

Provided and/or discovered by
1, 5) Reported by the vendor
2, 3, 4) The vendor credits Matthew Daley

Original Advisory
XSA-12:
http://lists.xen.org/archives/html/xen-announce/2012-09/msg00000.html

XSA-13:
http://lists.xen.org/archives/html/xen-announce/2012-09/msg00001.html

XSA-14:
http://lists.xen.org/archives/html/xen-announce/2012-09/msg00002.html

XSA-16:
http://lists.xen.org/archives/html/xen-announce/2012-09/msg00005.html

XSA-17:
http://lists.xen.org/archives/html/xen-announce/2012-09/msg00003.html

Deep Links
Links available to Secunia VIM customers