guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.
https://xenbits.xenproject.org/xsa/advisory-385.txt
Source: MITRE
Published: 2021-11-24
Updated: 2021-12-16
Type: CWE-770
Base Score: 7.8
Vector: AV:N/AC:L/Au:N/C:N/I:N/A:C
Impact Score: 6.9
Exploitability Score: 10
Severity: HIGH
Base Score: 8.6
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Impact Score: 4
Exploitability Score: 3.9
Severity: HIGH