Kernel software installed and running inside a Guest VM may exploit memory shared with the GPU Firmware to write data into another Guest's virtualised GPU memory.
Exploitability
AV:LAC:LPR:LUI:RScope
S:CImpact
C:HI:HA:N7.9/CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:NOther