The MSI-X MMIO support in hw/pci/msix.c in QEMU (aka Quick Emulator) allows local guest OS privileged users to cause a denial of service (NULL pointer dereference and QEMU process crash) by leveraging failure to define the .write method.
Exploitability
AV:LAC:LPR:HUI:NScope
S:CImpact
C:NI:NA:H6/CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H