The Linux kernel before 2.2.19 does not have unregister calls for (1) CPUID and (2) MSR drivers, which could cause a DoS (crash) by unloading and reloading the drivers.
Certain operations in Linux kernel before 2.2.19 on the x86 architecture copy the wrong number of bytes, which might allow attackers to modify memory, aka "User access asm bug on x86."