arch/x86/kernel/paravirt.c in the Linux kernel before 4.18.1 mishandles certain indirect calls, which makes it easier for attackers to conduct Spectre-v2 attacks against paravirtual guests.
http://lists.opensuse.org/opensuse-security-announce/2019-05/msg00043.html
https://access.redhat.com/errata/RHSA-2019:2029
https://access.redhat.com/errata/RHSA-2019:2043
https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.1
https://github.com/torvalds/linux/commit/5800dc5c19f34e6e03b5adab1282535cb102fafd
https://lists.debian.org/debian-lts-announce/2018/10/msg00003.html
https://twitter.com/grsecurity/status/1029324426142199808
https://usn.ubuntu.com/3775-1/
https://usn.ubuntu.com/3775-2/
https://usn.ubuntu.com/3776-1/
https://usn.ubuntu.com/3776-2/
https://usn.ubuntu.com/3777-1/
https://usn.ubuntu.com/3777-2/
https://usn.ubuntu.com/3777-3/