USN-3690-1 provided updated microcode for AMD processors to address CVE-2017-5715 (aka Spectre). Unfortunately, the update caused some systems to fail to boot. This update reverts the update for Ubuntu 14.04 LTS.
We apologize for the inconvenience.
Original advisory details:
Jann Horn discovered that microprocessors utilizing speculative execution and branch prediction may allow unauthorized memory reads via sidechannel attacks. This flaw is known as Spectre. A local attacker could use this to expose sensitive information, including kernel memory.
This update provides the microcode updates for AMD 17H family processors required for the corresponding Linux kernel updates.