CVE-2019-19580

An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS
users to gain host OS privileges by leveraging race conditions in pagetable
promotion and demotion operations, because of an incomplete fix for
CVE-2019-18421. XSA-299 addressed several critical issues in restartable PV
type change operations. Despite extensive testing and auditing, some corner
cases were missed. A malicious PV guest administrator may be able to
escalate their privilege to that of the host. All security-supported
versions of Xen are vulnerable. Only x86 systems are affected. Arm systems
are not affected. Only x86 PV guests can leverage the vulnerability. x86
HVM and PVH guests cannot leverage the vulnerability. Note that these
attacks require very precise timing, which may be difficult to exploit in
practice.

Notes