Xen 3.3.x through 4.5.x and the Linux kernel through 3.19.1 do not properly restrict access to PCI command registers, which might allow local guest OS users to cause a denial of service (non-maskable interrupt and host crash) by disabling the (1) memory or (2) I/O decoding for a PCI Express device and then accessing the device, which triggers an Unsupported Request (UR) response.

The xsave/xrstor implementation in arch/x86/include/asm/xsave.h in the Linux kernel before 3.19.2 creates certain .altinstr_replacement pointers and consequently does not provide any protection against instruction faulting, which allows local users to cause a denial of service (panic) by triggering a fault, as demonstrated by an unaligned memory operand or a non-canonical address memory operand.

arch/x86/kernel/entry_64.S in the Linux kernel before 3.19.2 does not prevent the TS_COMPAT flag from reaching a user-mode task, which might allow local users to bypass the seccomp or audit protection mechanism via a crafted application that uses the (1) fork or (2) close system call, as demonstrated by an attack against seccomp before 3.16.