An issue was discovered in Xen through 4.11.x allowing x86 guest OS users to cause a denial of service or gain privileges because grant-table transfer requests are mishandled.
https://xenbits.xen.org/xsa/advisory-284.html
https://www.debian.org/security/2020/dsa-4602
https://seclists.org/bugtraq/2020/Jan/21