Important product update: Fixes for CVE-2018-3639 and CVE-2018-1087 in virtual machines; Virtuozzo 6.0 Update 12 Hotfix 26 (6.0.12-3707)

This hotfix provides security fixes for the hypervisor part of Virtuozzo 6.0 Update 12.
Vulnerability id: CVE-2018-1087
A flaw was found in the way the Linux kernel’s KVM hypervisor handled exceptions delivered after a stack switch operation via Mov SS or Pop SS instructions. During the stack switch operation, the processor did not deliver interrupts and exceptions, rather they are delivered once the first instruction after the stack switch is executed. An unprivileged KVM guest user could use this flaw to crash the guest or, potentially, escalate their privileges in the guest.

Vulnerability id: CVE-2018-3639
An industry-wide issue was found in the way many modern microprocessor designs have implemented speculative execution of Load & Store instructions (a commonly used performance optimization). It relies on the presence of a precisely-defined instruction sequence in the privileged code as well as the fact that memory read from address to which a recent memory write has occurred may see an older value and subsequently cause an update into the microprocessor’s data cache even for speculatively executed instructions that never actually commit (retire). As a result, an unprivileged attacker could use this flaw to read privileged memory by conducting targeted cache side-channel attacks.