Multiple denial of service vulnerabilities have been discovered in the xen hypervisor. One of the issue could even lead to privilege escalation from guest to host. Some of the recently published Xen Security Advisories are not fixed by this update and should be fixed in a future release. CVE-2011-3131 : DoS using I/OMMU faults from PCI-passthrough guest A VM that controls a PCI[E] device directly can cause it to issue DMA requests to invalid addresses. Although these requests are denied by the I/OMMU, the hypervisor needs to handle the interrupt and clear the error from the I/OMMU, and this can be used to live-lock a CPU and potentially hang the host. CVE-2012-4535 : Timer overflow DoS vulnerability A guest which sets a VCPU with an inappropriate deadline can cause an infinite loop in Xen, blocking the affected physical CPU indefinitely. CVE-2012-4537 : Memory mapping failure DoS vulnerability When set_p2m_entry fails, Xen"s internal data structures can get out of sync. This failure can be triggered by unusual guest behaviour exhausting the memory reserved for the p2m table. If it happens, subsequent guest-invoked memory operations can cause Xen to fail an assertion and crash. CVE-2012-4538 : Unhooking empty PAE entries DoS vulnerability The HVMOP_pagetable_dying hypercall does not correctly check the caller"s pagetable state, leading to a hypervisor crash. CVE-2012-4539 : Grant table hypercall infinite loop DoS vulnerability Due to inappropriate duplicate use of the same loop control variable, passing bad arguments to GNTTABOP_get_status_frames can cause an infinite loop in the compat hypercall handler. CVE-2012-5510 : Grant table version switch list corruption vulnerability Downgrading the grant table version of a guest involves freeing its status pages. This freeing was incomplete - the page are freed back to the allocator, but not removed from the domain"s tracking list. This would cause list corruption, eventually leading to a hypervisor crash. CVE-2012-5513 : XENMEM_exchange may overwrite hypervisor memory The handler for XENMEM_exchange accesses guest memory without range checking the guest provided addresses, thus allowing these accesses to include the hypervisor reserved range. A malicious guest administrator can cause Xen to crash. If the out of address space bounds access does not lead to a crash, a carefully crafted privilege escalation cannot be excluded, even though the guest doesn"t itself control the values written. CVE-2012-5514 : Broken error handling in guest_physmap_mark_populate_on_demand guest_physmap_mark_populate_on_demand, before carrying out its actual operation, checks that the subject GFNs are not in use. If that check fails, the code prints a message and bypasses the gfn_unlock matching the gfn_lock carried out before entering the loop. A malicious guest administrator can then use it to cause Xen to hang. CVE-2012-5515 : Several memory hypercall operations allow invalid extent order values Allowing arbitrary extent_order input values for XENMEM_decrease_reservation, XENMEM_populate_physmap, and XENMEM_exchange can cause arbitrarily long time being spent in loops without allowing vital other code to get a chance to execute. This may also cause inconsistent state resulting at the completion of these hypercalls.