The compat_iret function in Xen 3.1 through 4.5 iterates the wrong way through a loop, which allows local 32-bit PV guest administrators to cause a denial of service (large loop and system hang) via a hypercall_iret call with EFLAGS.VM set.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 22.9%